Human Origins Hall – Bio on the Mall, Part 2

Before I left the U.S. Botanic Gardens last Thursday, I took a stroll through the rooms of cacti, banana trees, jungle plants, and my personal favorite, the orchids. After taking one last look at the corpse flower (it’s blooming now, by the way!), I headed over to the Smithsonian Institution’s National Museum of Natural History. I’ve been there many times, as a visitor and a former intern, but it always manages to draw me back again.

First, I looked into one of the newer permanent exhibits, the Human Origins Hall. This exhibit takes visitors on an exploration from early human evolution all the way to the challenges that modern humans face. I’m no anthropologist, but the exhibit distills what is clearly a large body of information into a few key concepts: humans have evolved over time, with changes in their appearance and behavior, and we continue to evolve today.

I admit, I’m one of those people who loves to comb through every word of an exhibit, but you don’t have to do that to enjoy the Human Origins Hall. The displays are interactive and engaging – there are sliding tabs to compare early and modern humans, touch-screens that answer questions on evolution, and even a “photo booth” that shows you what you would look like as an ancient human.

For a couple of hours while I was at the museum, Dr. Briana Pobiner, an anthropologist with the Smithsonian Institution, stood at a small cart in the middle of the Human Origins Hall. She was part of a museum program called “The Scientist Is In.” For a couple hours on certain days, a scientist stands in an exhibit hall, answering visitor questions and discussing their area of research – in Dr. Pobiner’s case, early human diets. I think this is a great program! It gives researchers the chance to share their enthusiasm with visitors, and to showcase research that all too often remains backstage at the Smithsonian.

I listened to Dr. Pobiner answer a lot of interesting questions on topics ranging from early human scavengers, to animal and plant domestication, to the modern “paleo diet” fad. Did you realize how much intelligence and resourcefulness it requires to be a successful scavenger? Or that many animal predators can’t break open bones for marrow, but humans can – and that marrow is an excellent source of high-fat nutrition? And it turns out that the real “paleo diet” was extremely diverse – as you might imagine, populations in different places and different situations had widely varying diets.

If you’re interested, you can look up the next “The Scientist Is In” event, or attend one of the other upcoming special events. For instance, on this Friday, the 26th of July, the Human Origins Hall will hold an open public dialogue on “how scientific and religious organizations can cooperate on the public understanding of human evolution.” Sounds pretty interesting!

The Human Origins Hall is visually interesting and informative; I recommend a visit. If you can’t make it to D.C., then you can always take a look at the exhibit web page.

Before I left the museum, I stopped in at one of the museum’s temporary exhibits. I’ll talk more about that next time!

Have you visited the National Museum of Natural History or the Botanic Gardens? Do you have a favorite place to visit on the Mall? Leave a comment below!

The Corpse Flower is Blooming!

On Thursday, I spent the day on the National Mall, where there are quite a few biology-related things worth a visit – even if it means braving the Washington, D.C. summer heat.

My first stop was at the U.S. Botanic Garden where – if you haven’t heard – a “corpse flower” is blooming! The titan arum, Amorphophallus titanum, is also known as the corpse flower or the stinky plant because it emits the scent of rotting meat to attract its pollinators. How enticing! So why is this exciting news? Well, the corpse flower can go for years or even decades without blooming (this particular one is seven years old, and this is its first flower), but when it does bloom, it produces the largest inflorescence in the world. The flower (technically an “inflorescence,” since the bloom contains multiple small flowers) can grow up to 12 feet tall!

Alas, when I arrived on Thursday, it was still just beginning to unfold. As of now, the bud is still sitting unopened, towering over camera-toting visitors like me. The flower should bloom in the next few days, however. In fact, you can visit the Botanic Garden’s “Return of the Titan” web page to watch a live-streaming video of the corpse flower as it unfolds! On the website, you can also find more information on this amazing plant.

After I left the Botanic Garden, I moved on to visit a few exhibits at my favorite place on the Mall, the National Museum of Natural History – but that’s a post for another day.

Book Review: The Demon-Haunted World by Carl Sagan

I recently read a book titled The Demon-Haunted World: Science as a Candle in the Dark, by renowned physicist and science writer Carl Sagan. It’s about aliens and witches, science and society – and it’s probably one of the most thought-provoking books I’ve read recently.

Sagan starts off by exploring why people hold unorthodox beliefs. Unusually for a book on science, The Demon-Haunted World does not treat investigations into things like alien abductions as unworthy of skeptical investigation, or beneath the notice of a “serious” scientist. Instead, Sagan devotes a great deal of effort to examining evidence of aliens, as well as other possible explanations for supposed alien sightings and abduction experiences. He then draws a comparison between modern belief in aliens and medieval European belief in witches and demons. They share certain external features (tales of terror and abductions in the night), but also, both are phenomena that exploded in the public consciousness, despite being rooted in evidence that crumbles upon closer inspection. Sagan does eventually conclude that stories of alien abductions – like demons – are better explained by more mundane causes, but he comes to this conclusion through careful, reasoned investigation. In other words, he uses scientific thinking.

The Demon-Haunted World is a more than a book on witch hunts and aliens; Sagan merely uses these as jumping-off points for exploring the role of science in society. Touching on topics ranging from the ethics of the hydrogen bomb to the importance of education, Sagan discusses what science and skeptical thinking truly are. What do they mean to people? How should we use them? And how do they affect our lives?

[S]cience – or rather its delicate mix of openness and skepticism, and its encouragement of diversity and debate – is a prerequisite for continuing the delicate experiment of freedom in an industrial and highly technological society. -pg. 431

Scientific thinking, Sagan argues, is essential to democracy. Unquestioning acceptance of a simple explanation, coupled with lack of critical thinking, can lead to false beliefs and irrational decisions, whether they be medieval witch hunts, modern beliefs in alien abductions, or bad public policy choices. We live in a political system where the people control their own governance; therefore, Sagan argues, we have a responsibility to understand the world we operate within, and to think critically about our actions, our policies, and our decisions. As he says in the final chapter, “real patriots ask questions.”

The subject matter can be serious at times, but the book keeps a lively tone. Sagan’s sense of wonder at science is infectious. The Demon-Haunted World is suffused with a feeling of awe at the world, passion for our own powers of discovery, and hope for the role science can play in our society.

Go read this book, if you haven’t already. It’s a good one.

Sagan, Carl. The Demon-Haunted World. New York: Random House, 1995.

The Other Father of Evolution

In my last post, I talked about how plant domestication emerged in multiple places at once. In this post, I’ll talk about a much more recent scientific advancement that also occurred to more than one person – evolution by natural selection!

Charles Darwin usually gets the lion’s share of the credit, but someone else came up with the same idea independently – Alfred Russel Wallace.

Wallace was a working-class scientist and collector of biological specimens, living in a time when most European scientists came from the upper reaches of society. In 1858, while on a collecting expedition in the Malay Archipelago, Wallace thought of the idea of evolution by natural selection. He outlined the basics of it in an essay, “On the tendency of varieties to depart infinitely from the original type,” and sent a copy of it to Darwin – Wallace knew that Darwin worked on evolution, but he didn’t know that Darwin had already conceived of the idea of natural selection about 20 years earlier.

Darwin recognized that Wallace’s essay might endanger his scientific priority on the idea he had been working on for the last two decades (but had yet to publish). However, he was unwilling to rush to publication now; he didn’t want to cheat Wallace out of getting credit. Conflicted, Darwin consulted his scientific friend Sir Charles Lyell, who – along with fellow scientist J. D. Hooker – decided to take matters into their own hands. They presented the idea of natural selection to the Linnean Society of London, using papers by both Darwin and Wallace, ensuring that both officially received equal credit for the idea.

Wallace went on to have a distinguished career, and during his lifetime, he was considered one of the greatest scientists of the era. So why do we now remember Darwin as the father of evolutionary biology, while most people have probably never heard of Wallace? For one thing, Wallace’s essay only outlined the bare bones of evolution by natural selection, whereas Darwin had been gathering evidence and working out the details for 20 years. The following year, when Darwin finally published all of this in his most famous book, On the Origin of Species, he was establishing the foundation for evolutionary theory, the unifying principle of all biology. (As a side note, I highly recommend taking a look at the book – Darwin was incredibly insightful, despite knowing nothing of genetics, DNA, or any of the other scientific discoveries of the last 150 years.)

Wallace also continued investigations into evolution, though he disagreed with Darwin on a number of points. For one thing, Wallace believed that human intelligence could not possibly have arisen through natural selection; he was also an avid explorer of spiritualism, which was popular in Victorian England. He was a prolific writer on topics ranging from science to spiritualism to social issues, and became a well-known public figure during his lifetime.

People are still debating over whether Wallace or Darwin truly deserves more credit for the idea of natural selection. However, I think I can state pretty firmly that Alfred Russel Wallace was an exceptional scientist who deserves more attention than he gets from the modern world.


Shermer, Michael. “In Darwin’s Shadow: The Life and Science of Alfred Russel Wallace: A biographical Study on the Psychology of History.” Oxford: Oxford University Press, 2002. This book, by noted skeptic Michael Shermer, is an interesting look at Wallace’s life as a scientist, public figure, and individual, as well as an exploration into the study of biography.

The Seeds of Plant Domestication

Humans have been cultivating domesticated plants for food for thousands of years, but when and where did agriculture begin? According to archaeological findings scattered across much of the Middle East, ancient people actually developed plant domestication in several places at once.

A recent Science article by Riehl, et al. describes archaeological findings at a site called Chogha Golan, which was occupied from about 12,000 to 9,800 years ago. Located in the foothills of Iran’s Zagros Mountains, Chogha Golan is one of a number of contemporaneous sites throughout the “Fertile Crescent” region. Many of these sites show signs of plant cultivation emerging about 10,500 to 11,500 years ago.

Researchers at the Chogha Golan site studied the contents of successive layers of strata, including the remnants of ancient plants, to determine biological change over time. The plant remains buried at Chogha Golan clearly document the process of domestication, from collection of wild-growing seeds to the cultivation of morphologically distinct, domesticated grains.

Domestication – plant or animal – is a gradual process. According to the archaeological record, humans started out by gathering wild plants, like the seeds of wild barley, wheat, or lentils, for food. Over time, people began to practice plant “management” – not quite agriculture, but a step beyond simple gathering – while selecting for those plants that have the most advantageous characteristics. Over hundreds of years of selective cultivation of the plants with the biggest seeds, stronger resilience, or whatever other characteristic people preferred, these cultivated varieties became distinct from their wild counterparts.

Interestingly, the archaeological evidence shows different varieties of domesticated plants emerging at different sites. Groups of ancient people probably developed their own local crops, domesticated from various species of wild plants, which created a wide variety of distinct, locally-developed domesticated plants.

The domestication of plants was a harbinger of huge changes to come for ancient humans. Chogha Golan shows an excellent record of this development – and it looks like it was only one of several agricultural origin points.


Riehl, Simone, Mohsen Zeidi, Nicholas J. Conard. “Emergence of Agriculture in the Foothills of the Zagros Mountains of Iran.” Science Vol. 341, Issue 6141, pp. 65-67.

Willcox, George. “The Roots of Cultivation in Southwestern Asia.” Science Vol. 341, Issue 6141, pp. 39-40.

What Causes Sore Muscles After Exercise?

Last week (and much of the week before) I’ve been unable to keep up on my posts, due to an ongoing home construction project. I won’t chatter on about the details, but suffice it to say, the project involved a lot of shoveling dirt and digging trenches. So, now that I’m finally able to return to my blog, I’ll talk about something I’ve experienced since the last time I posted – muscle soreness!

Most of you have probably felt it at some point, whether you’re a casual gardener or a professional athlete – you feel great, if a little tired, right after a new workout, but a day or two later, your muscles grow stiff and sore, only to return to normal again within the week. So what’s going on here? Why do you feel fine right after working out, but sore hours later?

This phenomenon is called “delayed-onset muscle soreness” (abbreviated as DOMS), and there are actually a number of proposed explanations. It occurs most frequently after strenuous, unfamiliar exercise, especially if muscles have been undergoing “eccentric” movement, in which muscle fibers are being stretched despite trying to contract at the same time.

One popular – and probably untrue – explanation for DOMS that you might have heard bandied about is lactic acid buildup. While it’s true that lactic acid builds up in muscles during strenuous exercise (it’s a byproduct of anaerobic respiration, which happens when muscles aren’t getting enough oxygen), the body clears that away relatively quickly; therefore, lactic acid buildup doesn’t explain soreness that persists days after exercise. In addition, lactic acid buildup also occurs in non-“eccentric”-type muscle movements, which don’t usually result in DOMS.

The most likely explanation for DOMS is actually a combination of several proposed explanations: muscle damage, movement of enzymes out of muscle cells, and inflammation. According to this hypothesis, muscle tissue is damaged by new or unfamiliar “eccentric” movements, which tear some membranes within and around the cells, allowing enzymes and other molecules such as calcium to leak into the surrounding area. This stimulates an inflammatory response from the body, which leads to the pain, stiffness, and weakness you might feel a few days after an unfamiliar workout.

DOMS doesn’t pose much of a problem in and of itself, since the soreness will go away and damage will heal on its own within a few days, but you should be careful about exercising sore muscles. DOMS can cause temporary muscle weakness, so your usual level of activity becomes proportionately more intense, putting you at greater risk for a more serious muscle strain. That’s not to say that muscle soreness should stop you from exercising – it’s just wisest to be careful.

Several review articles have looked over possible ways to treat or prevent DOMS, but they found no clear standout treatment strategy. There have been a lot of studies looking into various treatments, but on the whole, these studies have been plagued by small sample sizes, shoddy research methods, and conflicting results. Applying ice and compression might help somewhat; the jury is still out on whether NSAIDs (non-steroidal anti-inflammatory drugs) are useful; massage, stretching, and nutritional supplements probably won’t do anything. Interestingly, the most effective treatment by far is light exercise, which will lessen the soreness and stiffness (though only for a little while). Furthermore, repetition of the same “eccentric” muscle movements will decrease DOMS over time, meaning that you might feel less sore after doing the same muscle movements in future workouts.

So if you feel stiff and sore from, say, spending a week shoveling dirt, then you might feel better if you went outside and shoveled a little more.

Cheung, Karoline, Patria A. Hume, Linda Maxwell. “Delayed Onset Muscle Soreness.” Sports Medicine Volume 33, Issue 2, pp. 145-164 (2003).
Connolly, Declan A.J., Stephen P. Sayers, Malachy P. McHugh. “Treatment and Prevention of Delayed Onset Muscle Soreness.” Journal of Strength and Conditioning Research Volume 17, Issue 1, pp. 197-208 (2003).

Cheetahs on the Run

Cheetahs have been making the rounds of science news lately. Famous for their speed, they have in the past been clocked at 29 meters per second (nearly 65 miles per hour), making them the fastest animals on land – but that’s old news. A new study by A.M. Wilson and colleagues delved deep into the mechanics of the hunt with five wild cheetahs in Botswana, and their findings were a little surprising.

The cheetah still holds onto its place as the fastest land animal – the researchers recorded an impressive top speed of 25.9 m/s, or about 58 mph – but it turns out that the cheetah’s dexterity and maneuverability, not its phenomenal speed, hold the secret to its hunting success.

Wilson, et al. outfitted five wild cheetahs with GPS tracking collars that also contained accelerometers, to capture and transmit data on the cheetahs’ movements. The researchers used the data to reconstruct the speed, acceleration, and maneuvering in each of 367 runs over the course of 17 months; they also tracked the terrain of each hunting attempt by overlaying the GPS data onto Google Earth.

When most people think of a running cheetah, they probably envision a high-speed chase through open grasslands. In reality, about half of the runs recorded in this experiment took place among shrubs or dense vegetation, and cheetahs hunted about as successfully in these environments as they did on open ground. Although each of the five cheetahs reached speeds of 20 m/s (about 45 mph) or higher at least once during the 17 month study, during most hunts they only got up to a leisurely 14.9 m/s (about 33 mph) – although that would still leave Olympic sprinters in the dust.

According to this study, a cheetah on the chase only runs at top speed for a second or two; once it pulls near its quarry, the cheetah decelerates, and this is where the chase reaches its critical moments. At a slower speed, the cheetah can employ its maneuvering prowess, using large claws, high-traction footpads, and a low posture to grip the ground and make sharp, fast turns, in order to subdue its agile prey. The deceleration phase of the chase is the most important – paradoxically, the researchers found that greater deceleration was correlated with greater likelihood of catching the prey in the end. Maneuverability is more important than speed in the final moments of a chase.

Cheetahs are undeniably powerful runners. The fibers in the running muscles of wild cheetahs shorten faster than fibers in similar-sized muscles in other running animals – the researchers mention racing greyhounds and horses, for comparison – giving cheetahs extraordinary power of acceleration. But in the end, the key to the cheetah’s chase isn’t in sheer power. It’s all in the control.