Fractals Within Us

 This is a special guest blog article by Jiyeong Kim, a 3rd year PhD student in Computational Physics Laboratory at Tampere University in Tampere, Finland. Her research topics are time-series analysis and nonlinear dynamics in biological and financial systems. She can be reached at jiyeong.kim@tuni.fi. 

When you think of the word fractal, you probably have certain images immediately coming to your mind: infinitely continuing patterns and swirls! I find them fascinating and quite beautiful, especially when they are created in nature. Common examples of fractals in nature are snowflakes, tree branches, and Romanesco broccoli. Now, these are geometric fractals, but the concept of fractals is not limited to geometry. 

 

Romanesco broccoli. Photo by Aurelien Guichard
Flickr: Borough Market

The definition of a fractal is a structure that displays self-similar patterns across different scales. For geometric fractals, the scale is spatial one, but the scale can also be time. Temporal fractals are fluctuations that are statistically similar over multiple time scale; that is, when you look at a fractal signal at different scales, whether it’s 3 minutes, 30 minutes, or 3 hours, the fluctuations are similar. This type of signals are also known as 1/f noise, or pink noise.

What’s really fascinating about the 1/f noise is that it appears in many biological systems, including us humans, and it also seems to play an important role in our health. The most famous example of 1/f noise is our heartbeat. Even though many people believe that our heart rate should be regular (apart from it changing due to activities such as exercise or sleep), this is far from the truth.

Take a look at the figure below. Can you guess which one belongs to a healthy person?

Which one belongs to a healthy person?
Image: Goldberger et al., PNAS February 19, 2002 99 (suppl 1) 2466-2472

The correct answer is B! If you got it right, I am very impressed. When we showed these graphs to a group of cardiologists, not everyone got it right either. A and C belong to patients with several congestive heart failure syndromes, and D to a patient with atrial fibrillation.

So our heart rate, it turns out, fluctuates in a very complex manner that is neither too regular nor too random--it’s fractal! Having a fractal structure is often related to the system’s robustness against external stress; that is, our heart can adjust to sudden changes better in the presence of fractal dynamics. Many scientists have confirmed the presence of fractality and its alteration due to aging and heart diseases. Though fractal analysis is not used yet in clinical practices, it has a great potential as a noninvasive diagnostic tool. Who knows? All the handy heart monitoring devices out there may soon add a feature that tells you how fractal your heart rate is!

Heartbeat is not the only thing that is fractal within us. Respiration rate, blood pressure, gait (stride-to-stride fluctuation), glucose level, gene expression, DNA sequences...the list goes on. One I find especially interesting is finger tapping.

When you tap your finger to a certain tempo, you can imagine that it won’t be perfect like a metronome. Its deviations from the intended beats (the metronome) have fractal structure. A similar phenomenon also occurs in drumming. When a drummer performs, no matter how hard he/she tries, there are always some deviations from the exact beat, which turn out to be also fractal. The importance of the fractal deviations in drumming was revealed in a survey. Between two humanized drumming samples, one with Gaussian fluctuations and the other with 1/f fluctuations, many preferred the latter. In other words, the presence of 1/f fluctuations makes music sound more human.

A recent study conducted with a real-world data analyzed the song I Keep Forgettin’ (1982) by Michael McDonald. The drummer in the song is Jeff Porcaro (1954-1992), who was a session musician behind many recordings of, e.g., Michael Jackson and Madonna, and a member of major rock bands Steely Dan and Toto. The song features Porcaro’s well-known single-handed hi-hat technique that is particularly smooth and groovy; it’s the really fast, high-pitched beats in the background, if you are listening to the song. Guess what they found? 1/f fluctuations in both intervals and amplitude. The study implies that behind the groovy feel of a good drummer is the naturally occurring fractal fluctuations in the rhythm.

What you also need to know is that the 16th notes Porcaro plays is about 150 ms apart, and deviation is only about 20 ms. That is, there should be no way that we can detect the deviations with our ears. But somehow we can tell from the groovy feel that something is there. So the ‘groove’ is somehow also related to how we perceive the timing and rhythm. Could it be related to the fact that the nerve spike intervals have fractal fluctuations?

We continue to discover fascinating fractal phenomena and there are still many questions to be answered. Many researchers are working towards unlocking the secrets of fractal dynamics in human body, in nature (temperature, precipitation, ozone level, climate dynamics), and in our society (internet traffic, highway traffic, stock market dynamics, they all exhibit fractal fluctuations!). One of the biggest question in the studies of fractal time series is certainly the origin of fractality. Recent studies, including my own, have shown that we can find fractal dynamics even at the cellular level; clusters of heart cells, grown from stem cells in laboratory, beat together spontaneously exhibiting fractal-like fluctuations in their beat rates without any neural input. Looks like we are full of fractals all the way down to our cells!

Sources:

https://www.sciencemag.org/news/2015/06/secret-groovy-drumming-may-be-math

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0127902#sec002

https://www.pnas.org/content/99/suppl_1/2466

I Dug Up a Camel: Part 2

Last week's blog post was about the history of camels in the American southwest and how I found myself at a prehistoric camel dig in the middle of eastern Arizona. This week I'm excited to show pictures from the dig and explain the process of taking an ancient camel skeleton out of the desert and into the lab. First, a quick summary of our camel. We estimate that it's about 2.2 to 2.4 million years old, it is one of three camels (and a turtle) found in a small area, it's a sub-adult camel, and its skeleton is complete, meaning that almost all of the bones, from the head to the tail, were found at the same time. All of these details make our camel a rare find, so we want to take extra special care of it.

Me in the field out at the camel dig site. The turtle shell is about
200 feet behind me, and the camel is about 15 feet in front of me.
PC: Jessica Noviello, Nov. 2018.

On a bright but cold Saturday morning, we piled into pickup trucks with our rock hammers, flathead screwdrivers, hats, jackets, and sunblock and drove out to the dig site. Our group numbered about 15 people, ranging in age from a young boy of 10 to Larry, our senior expert from the local Bureau of Land Management Office. Most of us were volunteers eager to get experience at a real paleontology dig. Two expert paleontologists from the Arizona Museum of Natural History also came along to supervise and give us geologic context. To go out on a dig like this, everyone needs to have at least some experience working with fossils, and everyone must be able to work together as a team, or else we run the risk of damaging or destroying the bones.

I spent most of my weekend working on excavating the camel. Larry had already spent time uncovering it, and previous volunteer teams had already taken the skull and neck, two of the legs, and the hips out of the field. Our goal for the weekend was to remove the torso, and maybe start on getting another leg out of the rock and sand. Others worked on excavating the turtle shell (carapace), a large dome that was roughly 2 feet in diameter. Still others spent time walking around looking for other bone fragments and maybe teeth, a process called prospecting.

Step 1: We used toilet paper and field "glue" to stabilize the fragile
parts of the camel torso. PC: Jessica Noviello, Nov. 2018.

There's a big difference between reading about digs and actually being on a dig. I think what surprised me most is how many everyday items are used in paleontology, the first example of which was toilet paper. After we removed the surrounding dirt from the torso but before we could wrap the bones in plaster, we first had to stabilize and protect them from the plaster itself. We did this by gently placing toilet paper on the particularly fragile bits of the camel torso and wetting the paper with a liquid mixture of water and acetate, which we called field "glue."

Dipping burlap strips into the plaster to lay on the camel torso.
PC: Jessica Noviello, Nov. 2018.

Next we had to wrap the torso up in plaster to protect it on its journey from desert to museum lab. One volunteer, Emelia, was in charge of making the mixture of plaster and water the exact right consistency, which she called "pancake batter." Another volunteer, Alex, was in charge of ripping up burlap cloth. These burlap strips were dragged through the plaster mix and laid on the torso. We applied at least two layers of burlap and plaster to the entire torso, taking special care around the fragile bits. Finally, we put two wood planks onto the top of the torso, which makes the torso easier to carry and move.

The camel torso ready to be flipped! Rock hammer and blue
stuffed dinosaur for scale. PC: Jessica Noviello, Nov. 2018.

Removing the torso wasn't as easy as just picking it up from the dirt, however. There was still half the torso connected to the dirt underneath the bit we had already excavated. The only solution, therefore, was to flip the torso over. We did this by literally hammering a long rod underneath the torso and using it as a lever. I left the more experienced volunteers to the flipping so I could film it. I was surprised at how quickly it happened. We spent hours preparing the torso, but the actual act of flipping only took about 3 seconds. It was as easy as lifting up on the lever, catching the torso, and lowering it down onto the tarp we had laid out. The tarp allowed us to pick up the entire torso without directly touching it, potentially putting pressure on a weak point in the plaster. Speaking from experience, the tarp made it much easier to carry the torso back out to the cars, though we still needed 4 people to do it.

After we flipped the torso, we were relieved to see that the rod hadn't hit any of the remaining bones, particularly the two legs that were wedged underneath the torso. We were basically drilling blind, so we got really lucky! Unfortunately, the entire torso didn't survive the flip, and some bits and pieces were left behind. We spent the rest of that Saturday closely examining the dirt that was left behind, searching for bone fragments or even some skin impressions. The biggest pieces that were left behind were the ribs, which needed their own plaster jacket before they were moved. You saw these in Part 1 of this blog post.

Bone fragments I picked up while prospecting. Notice the
slight purple tinge and the shiny nature of the bones.
PC: Jessica Noviello, Nov. 2018.

By Sunday there wasn't much left to do on the camel, so I jumped between excavating the turtle shell and prospecting. At first I had a terrible time prospecting. The bone fragments were small and fragmented, so they camouflaged perfectly with the surrounding gravel. I quickly grew frustrated. Thankfully, another member of the Southwest Paleontological Society, Jenny, found a small area that had a bunch of bone fragments, so she called me over to help. I always thought that people exaggerated when they say "once I found one, I easily found tons more," but that's exactly what happened. The bone shards had a slightly purple tinge and a shiny luster that the dull gravel lacked. Once I knew what I was looking for, I couldn't walk two steps without finding more. We carefully put all the fragments into Ziploc bags and labeled them clearly so we had a good record of our data. These bones and bone fragments are true data, evidence of ancient life and a world that doesn't exist anymore. We don't get a second chance to find these if they are lost or destroyed, so we take the process seriously.

Soon after we packed up and covered the remainder of the camel with sand, to be dug up by future groups. The rest of the camel and the turtle headed back to Mesa, where more volunteers would remove the plastic and clean up the bones. I had a great time going out on my first paleontology dig, and if I wasn't in a desperate rush to finish my PhD this spring, I'd be going out again to finish the job. If you are interested in participating in a paleontology dig, I'd first suggest reading up on the subject, and then reaching out to a local museum to get experience working with fossils or in a lab. It is definitely a special experience, and one I am so thankful to have. At the very least, it makes for a great adventure story!

Me digging out the camel torso and preparing it to be flipped.
This is why we use flathead screwdrivers!
PC: Jessica Noviello, Nov. 2018.

I Dug Up a Camel: Part 1

Sometimes the best science opportunities suddenly appear in front of you. In those instances, the best thing to do is say yes and embrace the experience that will one day make a grand adventure story. In November 2018, one of these opportunities knocked me off my feet, literally.

I was training in my Krav Maga class with my partner, an older man named Sherman, and a fellow graduate student, Mariah. We were working on defending against aggressive knife techniques, and one of the defenses ends up with the attacker on the ground, which is how I found myself looking up at my partners with the wind knocked out of me. As I stood up and caught my breath, Sherman asked Mariah and me if we liked paleontology. Turns out Sherman is the President of the Southwest Paleontological Society (SPS), and because he knew that Mariah and I are geology graduate students, he invited us both out to a paleontology dig in eastern Arizona in mid-November. A little over a week later I was in a car driving out to a campground in Safford, Arizona. The hunt for bones was on! Our quarry: a prehistoric camel.

The view from our campground on this dig near Safford, AZ.
PC: Jessica Noviello, 2018.

Our housing at the campground. I was prepared for a tent, but this works too!
PC: Jessica Noviello, 2018.

 Camels have a long history in Arizona that begins 45 million years ago in the Eocene period. Back then, Arizona was a rainforest, and the place where a small, deer-like animal made its appearance in the fossil record: Protylopus. This is the earliest known camel, and its discovery surprised paleontologists. Modern camels, and even most fossil camels, have cushioned, wide feet to help them move over unstable terrain like sand and grassland gravel. But Protylopus walked on four dainty toes on each foot. As southwest North America changed from rainforests to grasslands, these feet put the Protylopus at a mobility disadvantage, and they couldn't overcome it. They eventually died out, but not before starting the lineages that would eventually lead to modern camels.

Artist's reconstruction of Protylopus in its habitat.
PC: WILLEMSVDMERWE and PBS: Eons.

Ancient camels eventually traveled north and west across the landbridge that spanned the Bering Strait, into Asia and Europe, where they became the modern camels we know today. North America and South America finally connected to form the isthmus of Panama around 3 million years ago, leading to a significant migration event called the Great American Interchange. Species that had evolved on one continent quickly moved to the other, including some camels. The camels that migrated south would eventually evolve into the ancestors of llamas and alpacas.

Our camel died after this Interchange event, sometime between 2.2 and 2.4 million years ago. It belonged to the Camelops genus, enormous animals that stood 11.5 feet tall as adults, almost twice as tall as today's camels. Camel skeletons and bones are fairly common throughout the American west, but our camel was unusual for a few reasons. One, our camel was a sub-adult, or a camel teenager; two, our camel was one of three found within a 200 span of an ancient river bed; and three, our camel was complete.

Rib bones of our camel. PC: Jessica Noviello, 2018.

In paleontology, a complete skeleton is one where all of the bones from the skull to the tail are found together, including the small bones found at the ends of the limbs. Turning a dead animal into a fossil takes a long time that ranges from thousands to millions of years depending on the environment. During this time period, scavengers can take bones away from the rest of the skeleton, and natural catastrophes like floods and mudslides can wash bones away.

Finding an entire skeleton is rare. Our camel is only the third complete camel discovered so far in the entire southwest! For this camel to also be a sub-adult makes it even more valuable, as it shows us exactly what that animal looked like at its stage in development as it grew from baby to adult. Its completeness indicates it was buried quickly, before anything could move the bones away. The fact that it was found with two other camels (and an ancient turtle too!) in an old riverbed points to a sudden event, like a flash flood, as the cause of death.

What was it like to dig up the camel? What are the steps involved? Who does stuff like that on their weekends? Find out in Part 2 of this blog post, coming next week!

Additional source:
"When Camels Roamed North America." PBS: Eons. November 20, 2018. https://www.youtube.com/watch?v=lJNoAE0UHzY

Scientific Conferences: AGU 2018

Happy New Year! We here at Science on Main hope you all have a great 2019!

For such a big part of an academic's life, conferences are rarely written about in the world of science communication. The to-do list of things just to attend conferences is long before an attendee even gets there: writing the abstracts, registering, making lodging and travel reservations, doing the proposed work, preparing the posters and oral presentations, and setting up meetings with colleagues are all part of conferences, and that's on top of the official stuff like sessions and workshops! But what happens at these conferences? What's the point of going to them at all? What are they like?

Granted, I can only speak to my own personal experiences at conferences, and each conference has its own particular feeling and style. Some things are similar for all though. It's usually hundreds, if not thousands of people who are all interested in a particular subject arriving at one location to speak to each other face to face. These are not just scientists, as the conferences I go to also have industry representatives who are there to both recruit new employees and sell their company's products. Conferences usually last for a whole work week, and if it's in a new city, I'll try to go at least one day early or stay a day later so I can do some exploring. I know I'm not the only one who does that. It's fun to explore a new city, or even a new country, like I did when I went to Rome, Italy to participate in a conference hosted by the European Space Agency.

The #AGU100 sign outside of the Exhibit Hall at this year's conference.

 The conference I went to in December 2018 was the American Geophysical Union (AGU) Fall Conference in Washington, D.C. It's by far the largest conference I go to because it spans all fields related to geoscience on Earth and elsewhere in the solar system (which is my field: planetary science). This year was special because it was AGU's centennial year, and they were definitely celebrating it. At least 27,000 scientists, exhibitors, students, professionals, volunteers, and organizers came to the nation's capital to share their results and network. Off the top of my head I can't list every discipline represented, but here are a few: planetary scientist, educators, atmospheric chemists, heliophysicists (they study the sun), seismologists, oceanographers, computer scientists, and statisticians. The other main conference I go to is only planetary science, and more specialized conferences mean fewer people attend. It's always good to dive deep into my subject, but I like AGU because it allows me to see techniques and ideas in other fields too.

Perhaps a third of the posters in the poster hall at #AGU100.
I'm guessing the whole thing was 1/4 mile long!

One of the best parts of conferences is how many events there are to go to at any given time, which means everyone can pick and choose what they want to attend. That choice can be a double-edged sword too, since going to one thing means saying no to potentially several others. I try to find friends who will either tweet or take extensive notes during their sessions, that way I never miss anything! This year at AGU I made sure to spend time in a few of the science communication workshops that the Sharing Science division puts on every year, including one that taught me the technical details of how to start a podcast. I came away invigorated and excited to pursue new ideas! This is in addition to the dozens of talks and posters I saw, the volunteering I did at the Arizona State University booth, and the one-on-one meetings I had, of course.

The AGU booth was selling stuffed owls in
sweatshirts. I couldn't resist. It was so cute!
I named him Dr. Whoot.

Speaking of the meetings, that's another major positive about conferences, especially for people who, like me, are approaching graduation and are looking to move to a new position at a new place. At AGU, I was able to meet with senior scientists from all over the country, including NASA Headquarters, to talk to them about potential positions for me. Conferences give young scientists a chance to display their body of work to the entire community and to make connections that will last years, perhaps decades, and many projects. I know of a post-doc who was offered a job the day after he gave his talk, which would not have happened without a conference. For people who are working on projects together, it is always more efficient to meet in person instead of emailing, as questions and concerns are addressed immediately. It improves the quality of the science done too!

Conferences are exhausting and crazy, but they are essential for science to grow and continue. To be able to talk to experts directly about their work increases my knowledge about the field and shows me what work needs to be done in the future. I also gained new collaborators and friends. I've only shared a fraction of the stories I got at this year's AGU, but I hope it was enough to show you a little of what a science conference is all about!

Some New InSight

Yesterday the NASA InSight mission successfully touched down on Mars. While it was the eighth NASA mission to reach the red planet's surface, it was the first in a few new categories: first mission to send information via cubesat orbiters, first mission to deploy instruments by itself upon reaching the surface, the first mission to launch from the west coast of the United States, and the first mission to drill into another planet. Sure, all those things sound cool, but why should we care?

Celebrations in the mission control room at JPL in Pasadena, CA after
confirmation of InSight's successful landing came through.

First, a bit of backstory. Every NASA mission that has flown in the past decade has been the winner in a multi-stage selection contest that NASA administrators run. We'll go into more detail in a later post since the process is fairly intricate, but the basics are that many missions submit their plans to a NASA request for proposals, then some of those are selected to move on and create prototypes and more precise mission plans, and from those only one mission is selected. The InSight mission was initially one of 28 mission proposals submitted to NASA in 2010. In May 2011, it became one of three selected from the whole pool to develop more details about the mission and begin some work on building and testing instruments. In August 2012, just days after the Curiosity lander successfully landed on Mars, the InSight mission was selected for development and flight.

InSight uses updated versions of technology that was first included on the Phoenix Mars lander, which successfully landed on Mars a decade ago (2008). To reduce the risks of future missions, NASA likes to select missions that make use of any instrument or mission piece that has already flown on a mission and worked. These missions components are called heritage pieces because they have been inherited down to a newer mission from an older one. The instruments are never exactly the same, even if scientists and engineers want them to be--manufacturers discontinue electronics, technologies improve, etc. Engineers are responsible for extensively testing every single mechanical aspect of the mission in a number of ways--extreme heat, extreme cold, and high radiation are only a few of the environmental factors that a space mission will experience in its lifetime. Of course, the instruments must not only survive, they need to work too, and it's much better to work out issues ahead of time than after launch.

Testing the robotic arm that will deploy the SEIS
instrument. Photo credit: NASA/JPL/Caltech

The seismometer on InSight is a good example of when extensive testing uncovered a problem that could have jeopardized the whole mission. The Seismic Experiment for Interior Structure (SEIS) instrument was built by the French National Space Agency CNES, and will be responsible for obtaining seismic data of Mars, which is effectively the reason that this mission was selected in the first place. Without it, the mission will not be able to collect any seismic information of Mars. Clearly, it was a key part of the mission. During testing, the engineers discovered multiple small leaks in its vacuum chamber that actually holds the seismometer. The leaks were severe enough that the mission's launch date was pushed back from March 2016 to May 2018. The overall cost of this delay was great in both time and money; it cost roughly $150 million to redesign the vacuum chamber, rebuild it, retest it, and pay for the time of the people who worked on it.

InSight launched on May 5, 2018 from Vandenberg Air Force Base in California, a location on the coast in between San Francisco and Los Angeles. Most NASA missions launch from Cape Canaveral in Florida, though some launch from the Wallops Island Flight Facility in Maryland, so InSight is unusual in this regard. Vandenberg was selected because of its good positioning to aim the spacecraft to enter the Mars atmosphere at the correct angle of 12 degrees. Any steeper and the mission would burn up. Any shallower and the mission would "bounce" off the top of the atmosphere and continue off into deep space, lost forever. It was 12 degrees, or failure. If anything, this illustrates to me that there are many precise calculations that go into making every single decision on a NASA mission, and one miscalculation could cost the whole mission.

After 6 months and 301 million miles, InSight finally entered Mars' atmosphere at a perfect 12 degree angle. Much has been written and said about what happened during the landing, so we'll point you to one of our favorites instead of rehashing it here. In about 3 month InSight will deploy its own instruments, including the seismometer and an instrument that will drill 16 feet down into Mars' crust to study the thermal environment of Mars beneath the surface.

A screenshot of the NASA InSight landing live-feed on November 26, 2018, showing the first picture InSight took of Mars' surface. The line in the background is the Martian horizon. The camera lens is still behind the dust cap in this image,  but that piece will be removed in a couple of days, after the dust settles.

Just to prove that it made it to the surface, InSight was programmed to take a couple of pictures at the surface and send them back to us here on Earth. Its relay system is the Mars Cube One (MarCO), an important first for this mission as well. MarCO are two 6U cube sat missions that was designed to relay messages back and forth between Earth and InSight on Mars while it was going through its landing process. What is a cube sat? Generally the larger a mission is, the more expensive it is. A cube sat is a mission that is roughly the size of a shoebox, and it's a type of mission that has become more popular in the past 5 years because they are small, quick and easy to build, and inexpensive. A "U" is a shorthand to refer to the size of a cube sat mission, where a U is a cube with 10 cm sides. A 6U cube sat, therefore, is one that is 30 cm long, 20 cm wide, and 10 cm tall. MarCO was a test to see how well cube sats would work in a deep space environment, one that it passed with flying colors. This will pave the way for future cube sat add-on components to larger missions and even individual cube sat missions (see LunaH-Map here).

All of these accomplishments were the results of years of hard work by its team members and the mission failures that happened before. We thank all the scientists and engineers who have study and do study Mars, and all the people who support them, and wish them all many congratulations! Here's to future breakthroughs on Mars!

Thanksgiving Plants

Last week we told you all about the domestication of the chicken-peacock, a.k.a. the turkey. Since there will be many vegetables present on Thanksgiving tables this week, it's only fair to talk about them too! Here are the histories of some of the most popular plants that we love to eat (or love to hate, we don't judge)!

Sweet potatoes, baked and delicious. Photo from: Food Network

Sweet potatoes: Ipomoea batatas, or the sweet potato, was first domesticated somewhere between the Orinoco River delta area of modern day Venezuela and the Yucatán Peninsula in Mexico around 5,000 years ago. The second name of the sweet potato, batata, is the original Taíno word for the plant, though the Quechua people in Peru call it kumar. Surprisingly, it is only distantly related to the white potato, and is a genetically different plant from a true yam. In fact, the sweet potato is fairly closely related to the morning glory flowers, and the flowers of a sweet potato plant are even called tuberous morning glories! As with most of the plants on this list, it was first introduced to Europe via Spanish conquistadors, and to China via Portuguese traders. Sweet potatoes were used around the world to supplement the lack of other food due to poor harvests or other natural events. For example, after the sweet potato was introduced to Japan in the early 1600s, it became an important plant that prevented starvation in years when the rice harvest was poor. It is a popular plant because it grows well and without pesticides in a variety of climates, though it will not survive the cold and requires roughly 36 inches of water a year to grow.

The Three Sisters plants. Image from:
University of Illinois Extension

Squashes and pumpkins: The domestication of squashes and pumpkins (all part of the genus Cucurbita) is one of the best known stories, and one of the oldest: there is archaeological evidence that puts the domestication of squashes before 10,000 years ago! The wild relatives of squashes produce fruit much smaller than what we know today, and the plants were bitter, even toxic. Only the intense domestication efforts of the indigenous people in Central America saved the squashes we enjoy today. These plants are highly adaptable, and grow in many diverse climates. The reason there are so many types is because they have been traded and transported around the world to many different places, and these plants needed to adapt to survive in their new habitats. The English word squash comes from the Naragansett word askutasquash (a green thing eaten raw), excellent evidence that the plant was able to adapt from its Mesoamerican origins to survive in Rhode Island!

An important point is that squash, beans, and corn are called the Three Sisters of plant husbandry because they are mutually beneficial organisms. Basically, they help each other grow so well that the native peoples in the Americas often planted the three of them together! Squash was the first of the Three Sisters to be domesticated, followed by corn and beans.

Corn: Corn was domesticated from maize by the indigenous peoples roughly 10,000 years ago in what is now southern Mexico. The word "maize" comes from the Spanish version of the original Taíno word for it: mahiz. While the consensus used to be that the Tehuacán Valley was the center of domestication, newer analyses show that the the nearby Balsas River Valley is the true origin point of what we know as corn. A study in 2002 showed that modern corn comes from a single domestication event of maize at least 9,000 years ago, and other studies put this date even earlier. Another study argued that knowledge of corn cultivation was spread through two different events thousands of years apart: one event spread corn cultivation down the Andes Mountains around 6,700 years ago, and the second event spread it across the rest of South America roughly 2,000 years ago. It was taken back to Europe by Spanish conquistadors, and quickly became a popular plant around the world because of its ability to grow in many climates, but it is very sensitive to cold and to droughts, and strong winds can uproot it because of its shallow root structure. Today there are many forms of corn, though most of them are grown for industrial purposes (corn ethanol, animal food, etc.).

Beans: Unlike other plants on this list, beans were known in Europe and around the world before any Spaniard set food on the American continents. The beans that are part of the Three Sisters, however, were originally domesticated in (as you may have guessed) Central America. Some bean remains in the Guitarrero Cave in Peru date beans there to 4,000 years ago, though genetic analysis has proved that those beans were merely cultivated there. Beans, along with corn and squash, gradually spread south as knowledge of their cultivation also spread. Beans need support as they grow, and growing them near corn stalks provided that support. Beans in return pull nitrogen from the air and put it in the ground for corn and squash to use. They grow best in the summer and with lots of water. Currently the genetic information for 40,000 species of beans are held in genebanks, but only 30 of those are actually eaten.

Cranberries on a bush. Photo from: FastGrowingTrees.com

Cranberries: Cranberries were domesticated very recently, only about 200 years ago in Cape Cod, Massachusetts. Before then they were wild plants that the Native Americans would collect and use in a variety of different ways, from preserving fish and meat to mixing them into a poultice to use on wounds. Because the cranberry is a relatively young domesticated plant, it hasn't changed much from its wild variety. Cranberries are closely related to blackberries, huckleberries, and the flower rhododendron (that part blows my mind), and distantly related to the fruits kiwi and persimmon. Most cranberries today are grown in the United States, specifically Massachusetts, Wisconsin, New Jersey, Oregon, and Washington, though they are also grown in five provinces in Canada, and parts of Europe and Chile. They are tough plants but do best in wet, cold regions. Cranberries also are high in polyphenolic antioxidants and have some anti-cancer properties. So, eat up!

We here at Science on Main wish you a very happy Thanksgiving, and thank you for reading!

Sources:
 Zhang, D.P.; Ghislain, M.; Huaman, Z.; Cervantes, J.C.; Carey, E.E. (1999). AFLP Assessment of Sweetpotato Genetic Diversity in Four Tropical American Regions (PDF). : International Potato Center (CIP) Program report 1997-1998. Lima, Peru: International Potato Center (CIP). 
 http://bioweb.uwlax.edu/bio203/2011/keesler_cole/
https://www.sciencedirect.com/science/article/pii/S1055790317301811 
https://www.smithsonianmag.com/smart-news/domestication-saved-pumpkin-and-squash-180957314/
"Origin, History and Uses of Corn". Iowa State University, Department of Agronomy. February 11, 2014.
Piperno, Dolores R. (2011). "The Origins of Plant Cultivation and Domestication in the New World Tropics: Patterns, Process, and New Developments". Current Anthropology. 52 (S4): 453–S470. 
Bitocchi, Elena; Nanni, Laura; Bellucci, Elisa; Rossi, Monica; Giardini, Alessandro; Zeuli, Pierluigi Spagnoletti; Logozzo, Giuseppina; Stougaard, Jens; McClean, Phillip; Attene, Giovanna; Papa, Roberto (3 April 2012). "Mesoamerican origin of the common bean (Phaseolus vulgaris L.) is revealed by sequence data". Proceedings of the National Academy of Sciences. 109 (14): E788–E796. 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4076063/
 

Turkey Tale

Soon, families in the United States will sit down around a table to consume a famous dish: the Thanksgiving Turkey. According to a study done by the National Turkey Federation (yes, it's a real thing), 88% of Americans eat turkey on Thanksgiving, which amounts to around 46 million turkeys every year for Thanksgiving alone. Turkey has become more popular as an alternative to red meat in recent years as more varieties of turkey burgers, sausage, and cold cuts are added to supermarkets, not to mention all the dishes you could make with leftover turkey after Thanksgiving! Yet how much do you really know about that bird on your plate?

Gobble gobble! What a beautiful bird. Photo from:
http://jacksbbq.com/home/turkey/

Turkeys are native to North America, mainly the vast area east of the Rocky Mountains and some parts of central Mexico. There are two species of turkey in North America: the familiar Meleagris gallopavo and the slightly-less-common ocellated turkey, Meleagris ocellata, which can only be found in Mexico's Yucatán Peninsula. The wild and domesticated turkeys belong to the same species, M. gallopavo, whose name literally means "chicken peacock." There are also five different subspecies of turkey that are found in different places of the United States, Mexico, and Canada: the eastern wild turkey, the Osceola (Florida) wild turkey, the Rio Grande wild turkey, Merriam's wild turkey, and Gould's wild turkey. 

Turkeys were first domesticated by the indigenous people of central Mexico in the modern-day states of Jalisco, Guerrera, and Veracruz around 2000 years ago. The birds were an excellent food source in both their meat and their eggs, and their feathers were used in decorations. Perhaps because of its silly appearance and perceived personality, the turkey was associated with the Aztec trickster god, Tezcatlipoca, a central deity of Aztec religion. New DNA analysis of turkey bones from the southwest United States suggest that a second, separate domestication event took place between 200 BCE and 500 CE. The evidence suggests that these turkeys lived in civilizations that were in central Arizona and New Mexico around and on the Colorado Plateau, which strongly implies that these animals were specifically bred by people instead of naturally migrating north from Mexico.

A ceramic whistle that looks like a turkey, from the Colima
shaft tomb culture in Jalisco, Mexico. 300 BCE–400 CE.

After the Spanish landed in the New World, they took some of the animals back with them to Europe.
The name turkey probably came from some of the birds coming into British ports via ships that traveled from the eastern Mediterranean Sea. They were incorrectly associated with the African guinea fowl, whose name back in the 1500s was the turkey cock, which was thought to have come originally from the country of Turkey. From there, the name stuck, and persists to the modern day. As a result of selective breeding in Europe, there are now many different varieties of turkeys, all part of the same original species. All of the domesticated turkeys today come from the original population that was domesticated in central Mexico thousands of years ago.

The names used to describe turkeys themselves are quite silly. Males are called toms, and females are called hens, which are actually normal names for birds. The two names for the young are rather odd though: poults and turkeylings (the best name I've ever heard for baby animals). The red pieces of flesh on the beak of the toms also have names. The flesh that connects to the bottom of the beak is called the wattle, and the flesh that connects to the top of the beak is called the snood. The average size of a turkey is 29.8 pounds and 3.5 feet long, but the largest turkey weighed 86 pounds and was 4.1 feet long!

An adorable turkeyling!
Photo by Kristie Gianopulos.

Finally, as you go to break the wishbone of the turkey after the meal, remember that the scientific name of that bone is the furcula, the "little fork" in Latin. The furcula is an ancient bone that is present in some theropod dinosaurs (think Velociraptor and Tyrannosaurus), which was used as evidence to show how birds are modern dinosaurs. Furcula in birds are used to anchor the muscles that power the wings and help the birds to fly, but in domesticated turkeys, those muscles aren't really needed. Two people breaking the bone as a sign of good luck is a tradition that dates back to the 1600s, though it was not called officially called a wishbone until 1860.

Personally, the most interesting thing I knew about turkeys before today was that Benjamin Franklin once thought they should have been the national bird instead of the bald eagle. Knowing what I know now, I have to agree with him: the turkey deserves a lot more attention than as a centerpiece once a year. Thank you for reading!

Sources:
http://extension.illinois.edu/turkey/turkey_facts.cfm
http://www.nwtf.org/hunt/article/wild-turkey-subspecies
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2840336/ <--Turkey DNA study
Webster's II New College Dictionary. Houghton Mifflin Harcourt 2005, ISBN 978-0-618-39601-6, p. 1217

November update

Thank you, readers, for your patience! Unfortunately there will not be an article this week, as the author's car got a flat tire and she spent all of her normal writing time fixing that. Part of being in grad school is making choices about how to spend time, and she needs to spend her work week on the stuff that will actually help her graduate.

There are at least three article topics lined up already for you, one of which will involve input directly from an outside source. We'll see you back here on Monday!

Blood Colors

First of all, we want to wish all of our readers a Happy (and safe) Halloween! Now, onto the science of blood.

Some of the most iconic monsters of all time seem obsessed with blood. Of course, vampires are the most famous among mythical creatures, but sharks can smell blood in the water from miles away, and vultures and ravens are attracted to the smell of blood and decaying flesh on land. All animals, with the exception of some very simple invertebrate animals like jellyfish, coral, and flatworms, have blood. An average human will have between 1 and 1.5 gallons of blood in their body at any time, and blood accounts for roughly 7% of the person's weight. It's an essential, valuable thing.

In general, human blood is made up of four major parts: white blood cells, plasma, platelets, and red blood cells. White blood cells, or leukocytes (luke-o-cites), are part of your body's immune system, and they are responsible for responding to microscopic threats that your body faces from bacteria, parasites, and infections. Platelets, or thrombocytes, are the small cells that stick together to form scabs and stop vessels from bleeding. They are the reason why all your blood doesn't spill out when you get a cut! Plasma is the colorless liquid that the other components are suspended in, and is mostly made of water.

Red blood cells, photographed with a scanning electron
microscope. Photo by the Wellcome Trust/Marc Turner.

Red blood cells are also called erythrocytes (air-ith-throw-cites), and they give blood its red color. Their job is to carry oxygen to every cell in your body. The cells then use the oxygen to create food and energy. The red blood cells also take waste away from the cells. As the red blood cells pass through organs like the liver and the kidneys, the waste is filtered out and eventually expelled from the body. Red blood cells are born in a person's bone marrow, and every cell will live roughly 120 days (about 4 months). Once they die, the spleen filters them out. The spleen also removes any red blood cells that are misshapen or damaged.

Of course, the color most associated with blood is red (I mean, it's right there in the name of the cells!). But blood actually comes in a rainbow of different colors, and it all has to do with the types of chemicals that it contains. Most vertebrates (animals with backbones) have red blood because our red blood cells contain hemoglobin, an iron-based protein. Each hemoglobin protein is made up of individual hemes, which bind iron particles. The iron particles in turn bind oxygen, which is then carried to the rest of the body. A deficiency in iron is called anemia, and is actually a fairly common deficiency in America. Since a low iron level makes it harder for blood to carry oxygen to cells, a person with anemia may become tired and short of breath more easily than someone with higher iron levels.

The different colors of blood. Image by Compound Chem.

Red blood is just one color though. Animals like horseshoe crabs have blue blood because instead of hemoglobin, they carry a protein called hemocyanin. This protein contains copper in place of iron, but it functions in much the same way. When hemocyanin-rich blood is carrying no oxygen, it is actually colorless! These animals have evolved a different type of blood circulation system that doesn't require as high of an efficiency rate, so copper sufficed.

Green blood is also seen in nature, but almost exclusively in worms and leeches. The protein that makes blood green is called chlorocruorin. Chlorocruorin also contains iron in its center, but one branch of the protein is replaced with a different chemical structure, which alters the entire protein. There is one lizard, aptly called the green-blooded skink, whose blood is indeed green. This lizard actually has true hemoglobin in its blood, but when its cells die, its body cannot break the protein down as far as our bodies can. The result is that the lizard's blood has a higher concentration of a by-product called biliverdin, which gives the lizard's blood a green color.

The green-blooded skink. Photo by Christopher Austin,
Louisiana State University Museum of Natural Science

One last shade of blood is bright violet-pink, which is the rarest color of all, occurring only in some species of marine worms. This blood's color is from a protein called hemerythrin, which is made of individual chemical units which all contain iron. This protein can only carry about 25% of the oxygen that hemoglobin could carry, unfortunately for the worms!

As much as modern science has learned about blood over centuries of study, the one thing no one can yet do is manufacture blood. Since blood is such a vital resource, and because it cannot be created, the only source of blood for people is other people. This is why blood drives are so necessary for people suffering from diseases or recovering from major accidents. If you are able and willing, please try to donate blood soon. Perhaps you can even make a joke about how the blood drive workers just wanted to suck out your blood!

Sources:
http://science.sciencemag.org/content/192/4237/335
https://www.compoundchem.com/2014/10/28/coloursofblood/
http://scienceline.ucsb.edu/getkey.php?key=2419
http://idahoptv.org/sciencetrek/topics/blood/facts.cfm
http://www.chp.edu/our-services/transplant/liver/education/organs/spleen-information

Fear of the Dark

Imagine a scary setting. Whatever kind of environment would make the hair on the back of your neck stand up straight and give you the feeling that someone–or something–is watching you, imagine it. I'll make a bet that the majority of these scenes are set sometime during the night. And why not? To some extent, everyone has a fear of the dark. Nyctophobia, or a deep and severe fear of the dark, is one of the more common phobias in humans. Where does this fear come from?

There is a lot of evidence to suggest that a fear of the dark is deeply rooted in our evolutionary history. 4.5 million years ago, the early ancestors of Homo sapiens were not the masters of the planet like the species is today. Instead, animals like Australopithecus afarensis were prey for bigger, stronger, faster animals. One advantage our ancestors had were that they were social animals, relying on each other to watch out for danger. This was an effective strategy, but only during the day. At night, their vision failed them. That meant they were vulnerable to attack. Truly, it was never a fear of the darkness itself, but the dangers the darkness concealed that fueled fear. The advent of anthropogenic fire certainly helped protect and defend us, but only if one stayed close to the flames. Eventually hominids started to build shelters, which added another layer of protection from both the elements and the predators.

The Tsavo Lions exhibit at the Field Museum in Chicago, IL
Photo credit: Jeffrey Jung

Even today, in areas where lions and humans live near each other, the risk of of a human being attacked by a lion is roughly 60% higher after 6 pm, according to a study published in 2011. This is partially due to the fact that lions generally hunt at night; the reasons for this are a combination of lower temperatures and an inherent advantage that predators have over their prey. One of the most vicious and notorious lion attacks were those committed by the Tsavo Lions, who preyed on the workers of the Kenya-Uganda Railway in 1898. These two lions were bold and their attack style was unprecedented: they would come into camp at night and drag workers from inside their tents. Any attempts to stop the lions from entering the camp with fire or fencing were thwarted by the lions. Workers left the construction site in large numbers and all progress on the railroad halted until British Lt. Col. John Henry Patterson hunted and killed both of the lions in December 1898.

The movie poster for the 1996 film about the
Tsavo Lion attacks in Tsavo, Kenya.

After their deaths, the legend of the Tsavo Man-Eaters grew. Patterson took their skins and made them into floor rugs, as was the style of the time. In 1924, the rugs were sold to the Field Museum of National History in Chicago, IL for a sum of $5000 (about $73,400 in today's money). The skins were in poor condition from a quarter century of being walked on, but now the skins and the skulls of the lions are on display in the lower level of the Field Museum. Isotopic analysis of the keratin in the bones and hair suggest that one lion ate the equivalent of 10.5 humans, and the other ate the equivalent of 24.2 humans. From Patterson's personal journals, the Tsavo lions killed between 28 and 31 people. The discrepancy in the numbers may reflect people the animals are known to have killed, but not necessarily eaten. The story of the Tsavo Lions continues today in modern entertainment, and appears in video games, movies, and books. My favorite is The Ghost and the Darkness, a 1996 movie starring Val Kilmer as Patterson.

What makes lions so adept at hunting at night? One of the many tools available to lions is their night vision. Cats need just 1/6th of the light humans need to see, giving them a significant advantage in low-light environments. Their eyes are also better at focusing that light more effectively than ours are. The curved cornea and large lens allow the cat eyes to take in all available light, and they also have a higher number of rods that are sensitive to dim light in their eyes than humans do. Cats also have a special layer in their eyes that hominids lack, called the tapetum, which directs light to sensory cells that bathes the retina in 50% more of the available light than the cells would receive otherwise. While a cat cannot see in fine detail or in as many colors as we can see, their eyes are designed to hunt, particularly at night. It's no wonder that cats are likely apex predators in their habitats, considering this and all their other tools!

Eye structure and function in cats by K. N. Gelatt,
seen in Merck Veterinary Manual.

The night is not just a place where scary things hide; it can hold discovery as well. It is needed to study distant stars and to see the Milky Way from Earth's surface. It is also associated with rest, sleep, and safety, a time when families gather in their homes and prepare for the next day. With all the artificial light available to humans now, true darkness can be hard to find, at least in the United States. Light pollution is a problem that affects migrating animals and can affect a human's ability to sleep soundly. Minimizing the disruption to our bodies' rhythms is why companies like Apple have "night modes" for their technological products. I myself have a rule that I am not allowed to look at my phone or computer screens after 9:30 pm, or else I sleep poorly and can hardly think the next day.

Perhaps the lesson here is that everything, even light, has a dark side. That nervousness I feel walking alone at night is just a normal evolutionary response that served my ancestors well, but it never stopped me from Trick-or-Treating after sunset when I was younger. There are still dangers in the dark, of course, but at least they are (probably) not lions anymore!

Sources:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0022285
https://www.sciencedirect.com/science/article/pii/S0149763410001399 
Kerbis Peterhans, J. C. & Gnoske, T. P. (2001). "The science of 'man-eating' among lions Panthera leo with a reconstruction of the natural history of the 'man-eaters of Tsavo'". Journal of East African Natural History. 90 (1): 1–40.
http://www.pnas.org/content/106/45/19040
The Man-Eaters of Tsavo and other East African Adventures by Lieut.-Col. J. H. Patterson

Cryptozoology

Now that it is most definitely October, we thought it'd be fun to talk about the science behind some of the classic horror stories associated with Halloween, and about some animals that are generally associated with the spooky, occult, or unknown. Until Halloween, we'll be focusing on these topics to help get everyone into the spirit! Our first topic is the study of hidden monsters: cryptozoology.

Cryptozoology is the name for the field that focuses on finding cryptids, or animals that, so far, only exist in folklore and oral traditions. Some examples of these unknown animals are Bigfoot (or Yeti in the Himalayas); Nessie, the Loch Ness Monster in Scotland; and the chupacabra of Mexico and the southwestern U.S. states, but it turns out there are hundreds of creatures that fit into the cryptid category. Because it does not follow the scientific method, a process where hypotheses are proposed, evidence is collected and analyzed, and conclusions are drawn that either reject or support the hypotheses, cryptozoology is considered a pseudoscience, halfway between zoology and the branch of cultural anthropology that focuses on folklore and legend.

A map showing some of the cryptids of American folklore and oral tradition.
From: https://www.hogislandpress.com/product/monster-map

I first heard of some of the animals in the graphic above from a television show that aired on Animal Planet. I used to wake up very early before school started, which meant my options for TV shows were limited. Animal Planet always had something on though, and for a while one of the shows I watched was Lost Tapes. Every episode focused on a different cryptid's story, going through the original folklore in between flashbacks from "lost tapes" that show a victim's interaction with one of the fearsome, mysterious animals. Every story was fictional, but some were done so well and were so unnerving that I think about them to this day.

The show only lasted for 34 episodes, unfortunately, and exposed its audience to monsters such as the Thunderbird, Wendigo, Hellhound, and the Jersey Devil. The descriptions of these animals and the legends behind them can be skin-crawling, and I think the show did an excellent job of presenting the monsters in a way consistent with the right levels of reverence and fear. I personally enjoyed learning about the history of the legends more so than seeing the flashback parts of the episodes, but sometimes they'd also share information about recent possible sightings of the animals. It always made me want to go out and try to find something on my own.

Luckily Animal Planet has another show about hunting a cryptid that I can watch instead of camping all over the country (even though I'll probably do that on my own anyway). This show is, of course, Finding Bigfoot. On the show a small team of Bigfoot enthusiasts go to towns where Bigfoot sightings have occurred and then attempt to have their own encounters. This team takes their work seriously, even though there is no concrete physical evidence of any kind of large ape living undetected in the continental U.S. and Canada. The team meet with local people who have stories to share, and then the team goes out into the area where the sightings occurred to recreate the encounter. They do this to figure out what kind of animal could fit the description the witness gives. A majority of the time, the team actually rules out Bigfoot as the culprit for an unusual sound at night or a quick glimpse in the woods, and instead attributes the encounter to a bear, elk, or deer.

The team also spend time walking around the woods at night, making Bigfoot calls and knocking on sticks as Bigfoot is thought to do. They use thermal imaging and night vision goggles to heighten their sense of sight and maximize any chance of seeing a Bigfoot. Their ultimate goal is to find definitive proof that Bigfoot exists, and the show exists to document their adventures. The probability that a large, bipedal primate (aka Bigfoot) has consistently escaped any kind of detection by modern humans is very small, but non-zero. This uncertainty fuels their curiosity and drives them to keep looking.

Model of Latimeria chalumnae in the Oxford Univ. Museum of Natural History.
Photo by: Ballista at the English Language Wikipedia

While it is unlikely that anyone will ever find hard evidence of Bigfoot's existence, it is important to acknowledge that there are still many things that science cannot answer. Wildlife biologists discover new species every year, and while the vast majority are new insects, invertebrates, and amphibians, sometimes a new mammalian or even primate species is found. Sometimes animals thought to be extinct reappear in the modern day; for decades, paleontologists thought the ceolacanth fish extinct since the Cretaceous, until one was caught off the east coast of South Africa on December 23, 1938. It was Marjorie Courtenay-Latimer, curator at the East London Museum, who recognized the unusual fish in the catch of a local fishing captain, and brought it to the world's attention. Today, there are coelacanths in museums around the world.

Any scientist needs to walk a razor's edge between keeping an open mind to all possibilities while carefully and critically examine all the evidence in front of them to find the best answer. Often this means that there are far more likely explanations for something than "Bigfoot did it," hence why the existence of these animals isn't in any way guaranteed. What is fascinating to me is seeing all the ways that humans have explained nature around them and passed stories down through the centuries, and how they have spread across cultures. It also reminds me that there is much left in our world to discover and investigate, some of it fairly nearby! I'd love to get a story about the Mogollon Monster this weekend when I go hiking. I guess you'll have to wait for next week's blog article to find out what happens!

Sources:
https://en.wikipedia.org/wiki/Lost_Tapes
http://aplostapes.wikia.com/wiki/Lost_Tapes_Wiki
https://www.animalplanet.com/tv-shows/finding-bigfoot/
http://www.dinofish.com/discoa.htm