When you watch a pitcher wind up and throw a fastball down the middle, or a quarterback step out of the pocket and make a successful long pass, you’re seeing millions of years of human evolution and adaptations in action.

Or so say researchers Daniel Lieberman and Neil Roach. Their study, published today in Nature, determines that this uniquely human trait—high speed and high accuracy throwing—originated with our ancestors Homo erectus, two million years ago.

Darwin speculated that by freeing up the arms, bipedalism may have enabled our hominin ancestors to hunt effectively using projectiles. But scientists had been unable to pinpoint the exact time throwing became viable.

“When we started this research,” Roach says, “we asked: How do we do it? What is it about our body that enables this behavior, and can we identify those changes in the fossil record?”

The researchers began by creating a complex model that incorporated current research about the biomechanics of throwing. Using that model, they were able to explore how morphological changes to the body—wider shoulders, arms that are higher or lower on the body, the ability to twist the upper body independently of the hips and legs, and the anatomy of the humerus—affect throwing performance.

They also studied 20 experienced human throwers during overhand baseball pitching, demonstrating that several derived anatomical features that enable elastic energy storage and release at the shoulder are central to our ability to throw powerfully and accurately. (Video is available of these mechanics on Harvard’s website.)

“We try to push these bits of anatomy back in time, if you will, to see how that affects performance,” Roach says. “The important thing about our experiments is that they went beyond just being able to measure how the restriction affects someone’s ability to throw fast and accurately—they allowed us to figure out the underlying physics. For example, when a thrower’s velocity dropped by 10 percent, we could trace that change back to where it occurred.

“In order to test our evolutionary hypotheses, we needed to link the changes we’d seen in the fossil record to performance in terms of throwing,” he continues. “This type of analysis allowed us to do that.”

This throwing ability was incredibly important for our ancestors, the researchers say. It helped them become more successful hunters and carnivores, paving the way for a host of later adaptations, including increases in brain size and migration out of Africa.

However, while speed and accuracy proved a crucial development for early hunters, the study’s authors warn that repeated use of this motion can result in serious injuries in modern throwers, especially in young baseball players, who often suffer from laxity and tearing in the ligaments and tendons of their shoulders.

“I think it’s really a case of what we evolved to do being superseded by what we’re now asking athletes to do,” Roach says. “Athletes are overusing this capability that gave early humans an evolutionary advantage, and they’re overusing it to the point that injuries are common.”

Image: Rick Dikeman/Wikipedia

This week, Zeray and his colleague David Green, of Midwestern University, have published a study in Science (the cover story, no less!) thanks to Selam and her shoulder blades. The researchers find that even though A. afarensis was bipedal, Lucy, Selam, and their kin also climbed trees.

When the Lucy skeleton was discovered in 1978, “there was no question that this creature was an upright walking species,” says Zeray. “The foot, the knee and pelvis are all very human-like.”

However, the upper body told a different story. The features were much more ape-like, including long, curved fingers.

At the time, says Zeray, scientists split into two groups. “One group said, ‘Yes, A. afarensis has ape-like features, but the species doesn’t need them for survival, it’s just retention, evolutionary baggage. They can’t be interpreted for function.” A function like tree climbing found in earlier human ancestors.

The second group interpreted the ape-like characters for their function: “they saw the lower body for bipedalism and the upper body for climbing,” Zeray explains. “This discussion went on for the past 35 years.”

Now Zeray and Green’s paper may help the second group’s debate.

When Zeray published the findings of Selam in 2006, he noted that Selam’s scapulae, or shoulder blades, were gorilla-like, but he didn’t attempt to interpret that finding. Mainly because even though the two shoulder blades were intact, they were completely buried in compacted sand. Zeray and Kenyan lab technician Christopher Kiarie had to remove the super-thin fossils from the rest of the skeleton. Sand grain by sand grain.

That sort of work doesn’t happen overnight. It took them 11 years! Once the scapulae were extracted, Zeray could analyze the fossil in a detailed fashion. He confirmed they were gorilla-like, but there still wasn’t enough information to interpret the findings. Then, he and Green began their collaboration.

Green works on living species, Zeray on fossil species. The team began to collect data on many living primates—humans, chimpanzees, gorillas and orangutans—juveniles and adults. They also looked at the Turkana Boy’s shoulder blades. This Homo erectus fossil provides the second earliest and most complete scapulae of our ancestors—1.5 million years-old. Selam, at 3.3 million years, provides the oldest.

After the researchers analyzed the data, they concluded that A. afarensis climbed trees. Their evidence? The shoulder blades were indeed ape-like anatomically. In addition, they found that Selam’s shoulder blades developed like modern apes, not like humans. In apes, the shoulder anatomy of juveniles and adults are similar, but in humans, the anatomy changes quite a bit between the young and old. Finally, Zeray and Green demonstrated that the way the bone and muscles were oriented—in an upward direction—allowed more flexibility for climbing.

Zeray offers an explanation for this adaptation. “This species was small—chimpanzee-sized—in a wild environment with just a few stone tools, surrounded by scavengers and predators. They needed to nest at night, provision themselves and evade predators and carnivores. That’s why they maintained climbing, even though they were bipedal.”

This finding offers a bigger picture of human evolution. “When we became humans, we did not just jump from tree and start running. It was progressive,” says Zeray.

“The Selam skeleton is a mine of information for years to come,” he continues. And not just for his research, but many others. He can’t predict what we might find with this fossil, but he can imagine the possibilities, “how the species behaved, moved, looked, developed, voiced.”

For his own research into Selam, he’s not looking for anything specific and has no expectations. Zeray lets the data dictate the results—as interesting things pop up, he’ll give them the attention they need. He’ll let the data Selam provides lead to the science.

Image: Zeray Alemseged/Dikika Research Project

The finding builds on research as early as the 1940s that found these whales sound like human children. In the 1970s, an animal at the Vancouver Aquarium was heard to say his own name, Lugosi.

This time, scientists at the National Marine Mammal Foundation (NMMF) conducted acoustic analysis of a beluga named NOC in their facility in San Diego. It all started in 1984 when staff began to notice some unusual sounds in the vicinity of the whale and dolphin enclosure. It sounded as though two people were conversing in the distance, just out of range of their understanding. They traced the sounds to NOC a bit later when a diver surfaced from the whale enclosure to ask his colleagues an odd question: “Who told me to get out?”

They recorded the whale’s sounds to reveal a rhythm similar to human speech and fundamental frequencies several octaves lower than typical whale sounds, much closer to that of the human voice.

In general, whales make sounds via their nasal tract, not in the larynx as humans do. But the scientists found that NOC had to vary the pressure in his nasal tract while making other muscular adjustments and inflating the vestibular sac in his blowhole—a tricky maneuver.

“Our observations suggest that the whale had to modify its vocal mechanics in order to make the speech-like sounds,” says Sam Ridgway of NMMF. “Such obvious effort suggests motivation for contact.”

Sadly, after 30 years at the National Marine Mammal Foundation, NOC passed away five years ago. But the sound of his voice lives on—listen here.

Image: Greg Hume/Wikipedia

An international consortium of researchers recently announced another milestone in the quest to unravel the genetic makeup of the human species. The project—ENCODE, for Encyclopedia of DNA Elements—is a collaborative effort among 440 researchers in 32 global institutions, coordinated by the National Human Genome Research Institute (NHGRI). The results of this international effort will stand alongside such research breakthroughs as Watson and Crick’s 1953 description of DNA’s double helix structure and the Human Genome Project’s 2003 complete sequencing of humanity’s 3.2 billion nucleotides.

ENCODE mapped more than four million non-coding regions of the genome that regulate and interact with protein-producing DNA. The scientific consortium also confirmed that 80 percent of the genome performs specific biological functions. This upends the previous consensus that long stretches of DNA were no more than “junk DNA.”

“This is one of the most important collections of information the world is trying to decode,” explains Brian Simison, head of the Academy’s Center for Comparative Genomics.

Not only does ENCODE solve a bit more of the human genome puzzle, but it offers the potential to accelerate medical research. “We’ve known for a long time that there is a genetic basis to many diseases,” says Simison. “What we didn’t realize is that the source of many diseases would be found in the vast regions of the genome previously known as junk DNA.”

While others describe the project as having found the on/off switches to our genes, Simison prefers the term ‘regulatory function.’

“We are learning that junk DNA has a regulatory role in dosage, duration, timing and other regulatory functions. Understanding these functions will transform Western medicine,” Simison adds. “ENCODE reveals that Western medicine is in its infancy.”

Simison points out that ENCODE is also altering our vision of the genetic composition of life. “Most people think all genetic material is passed down to us by our direct ancestors. Actually,” Simison explains, “the human species is filled with ‘fossil DNA’ transferred to us from viruses.”

As an example, Simison describes a retrovirus that has inserted its DNA into a person’s genome. These endogenous retroviruses (ERVs) are found throughout the genome and it is now believed that some of these have been repurposed.

Finally, Simison explains that it’s not just what ENCODE found but how they found it that is significant.

“The wow factor is enormous,” Simison laughs. As the National Institute of Health reports, hundreds of international researchers performed more than 1,600 sets of experiments on 147 types of tissue with technologies standardized across the consortium.

“Although technology has improved, no single institution could have analyzed the genome data on its own,” Simison remarks. “You need many people sifting through the many layers of data to decode the human genome.”

“I believe it is a positive development that so many nations are sharing this knowledge,” he said, lauding the consortium for its cooperative methods. “These illustrate how the path towards lofty ambitions is often as fruitful as the objectives themselves. Unlike the U.S. space program, the Human Genome Project and ENCODE were international projects where the benefits that emerge are shared with and benefit the world.”

ENCODE’s results were published last month in a wide range of scientific journals and posted online to ensure transparency and public access. To learn more, review the publications here.

Barbara Tannenbaum is a science writer working with the Academy’s Digital Engagement Studio. Her work has appeared in the New York Times, San Francisco Magazine and many other publications.

The authors of the paper sequenced the entire genomes of five members of each of the following hunter-gatherer populations: forest-dwelling, short-statured Pygmies from Cameroon, and click-speaking Hadza and Sandawe individuals from Tanzania.

The fascinating findings tell us more about human origins and prove to be a bit controversial, so I wanted to get more information from the Academy’s expert in human evolution, Zeray Alemseged. Zeray’s studies of early human remains have been published in prominent journals and garnered him worldwide attention. (PBS’s NOVA filmed an extensive interview with him here last spring, in addition to being on the covers of Nature and National Geographic.)

Zeray says these populations are not well studied and their isolation offers a new view on the human genome. Their unique diets, stature and culture also enable scientists to potentially link specific attributes to genetic markers, he adds.

The researchers used an in-depth method that involves sequencing each strand of DNA more than 60 times on average. This redundancy makes the sequencing highly accurate, giving the geneticists confidence that any mutations they identify are real and not errors.

Their results suggest that different human populations evolved distinctly in order to reap nutrition from local foods and defend against infectious disease. They also identify new candidate genes that likely play a major role in making Pygmies short in stature.

Scanning these sequences, the researchers found 13.4 million genetic variants or mutations—locations in the genome where a single nucleotide differed from other human sequences—and astonishingly, 3 million are new to science.

These new variants can represent the gene expressions unique to these populations, Zeray explains. This study is quite significant in making these genetic links to function and attributes that are phenotypic.

Zeray reminds us that these genetic studies aren’t just for mapping our ancestry, but also for mapping our future. He offers two separate examples—first, personalized medicine could tailor to specific gene regions. Second, “If we can link variants to diet, isolation and environment,” Zeray says, citing this current study’s examples, “then we can also understand what future climate change might look like for our species and how to prepare for it.”

Finally, the study finds genetic evidence that these direct ancestors of modern humans may have interbred with members of an unknown ancestral group of hominins. Zeray remarks that this particular finding—of a potential new species—reminds us why, in this technological age, paleoanthropology is a transdisciplinary endeavor requiring both fossil discovery AND genetic research.

So he’ll wait for more evidence, along with the rest of us…

The jaws discussed in the study are likely 1.8 to 2 million years old. But the story begins much more recently—in 1964, when Mary and Louis Leakey found a skull. They described it as Homo habilis, one of the oldest species of the Homo genus and possibly the first stone tool-maker.

Then in 1972, another skull was discovered. This one was somewhat similar to H. habilis, but larger, and seemingly with a flatter face. Many researchers attributed it to a separate species, Homo rudolfensis.

But not all paleoanthropologists agreed. Some thought it was just a larger version of H. habilis, perhaps showing the male-female sized difference known as sexual dimorphism that is common in primates. They also believed that the flattened aspect of H. rudolfensis’ face wasn’t indicative of its true shape—that it wasn’t flat after all. These scientists argued this skull didn’t belong to a separate species.

And the arguments have continued for 40 years. However, with the new study, researchers report on a discovery of another skull (face, actually) and two jaws. These fossils provide more evidence, it seems, for the existence of H. rudolfensis as a separate species.

Not that this ends the arguments. Instead, it seems to have provided more fuel for the fire! (See headlines above.)

Why does it matter so much? Because it all centers on human evolution—determining where we come from and where we go to from here. Some scientists look at human evolution as a linear straight line. But with H. habilis and H. rudolfensis (and a third species, Homo erectus) potentially co-existing at the same time, what does that say about our lineage? We shouldn’t be surprised, Zeray says, especially if we consider the way in which plants and other animals have evolved—it simply means that we are part of them and diverse. The possibilities are intriguing!

Image: Fred Spoor/National Museums of Kenya

Giant Rogue Python Swallows Deer Whole

It’s a link to a LiveScience article about a python in Florida doing just that. And it’s not unusual. Adult Burmese pythons can get as big around as telephone poles and grow to 27 feet long. They can eat prey as large as the aforementioned deer, sustaining the snake for months at a time.

When the pythons eat prey this large, interesting things happen to their insides. Their internal organs enlarge. In fact, previous studies show that the hearts of Burmese pythons can grow in mass by 40 percent within 24 to 72 hours after a large meal, and that metabolism immediately after swallowing prey can shoot up by fortyfold. (The snake’s heart goes back to normal size after a few days.)

According to ScienceNOW, this has long fascinated researchers.

Turning weak mammalian hearts into something similar to the pythons’ behemoths has been the longtime goal of many biomedical researchers. Bigger, stronger hearts can improve the flow of blood in people with cardiac disease.

Human hearts can grow—in both good and bad ways, says Leslie Leinwand, a cardiology researcher with the University of Colorado and the Howard Hughes Medical Institute. Although cardiac diseases can cause human heart muscle to thicken, heart enlargement from exercise is generally beneficial.

“Well-conditioned athletes like Olympic swimmer Michael Phelps and cyclist Lance Armstrong have huge hearts,” she states. “But there are many people who are unable to exercise because of existing heart disease, so it would be nice to develop some kind of a treatment to promote the beneficial growth of heart cells.”

Enter the python heart. Leinwand set up experiments in her lab to test python heart growth. Her team confirmed that something in the blood plasma of pythons was inducing positive cardiac growth. They then began looking for specific changes by analyzing proteins, lipids, nucleic acids and peptides present in the fed plasma.

They used a technique known as gas chromatography to analyze both fasted and fed python blood plasma, eventually identifying a highly complex composition of circulating fatty acids with distinct patterns of abundance over the course of the digestive process.

The researchers then tested the fed-python composition on a fasting python and the fasting python’s heart grew, without eating anything.

Next, the team tried the mixture on mice. The animals were hooked up to “mini-pumps” that delivered low doses of the fatty acid mixture over a period of a week. Not only did the mouse hearts show significant growth in the major part of the heart that pumps blood, but the heart muscle cell size increased, without showing an increase in heart fibrosis—which makes the heart muscle more stiff and can be a sign of disease. There were also no alterations in the liver or in the skeletal muscles.

“It was remarkable that the fatty acids identified in the plasma-fed pythons could actually stimulate healthy heart growth in mice,” lab postdoc Brooke Harrison says. The team also tested the fed-python plasma and the fatty acid mixture on cultured rat heart cells, with the same positive results.

Will it have the same effect on humans? More experiments are required. But as the New York Times reports:

…the day may come when doctors literally prescribe snake oil for heart disease.

The research was published last week in Science.

Thirty years ago, a farmer discovered an adult male mastodon skeleton in Washington state. At the time, archeologist Carl Gustafson excavated the fossil and found some peculiar things about it. Ed Yong explains in the Guardian:

[He] noticed a pointed object embedded in its rib. Gustafson took a fuzzy x-ray and interpreted the object as a projectile point made of bone or antler… By dating organic matter around the fossil, he estimated that it was about 14,000 years old.

Other researchers challenged the man-made instrument and date—one reason was that it pre-dated the Clovis culture by about 1,000 years. Clovis is the name given to the distinctive tools made by people starting around 13,000 years ago. Gustafson’s finding would have rewritten the history of people on our continent.

Technology has changed quite a bit since the discovery of the mastodon bone thirty years ago. Enter Michael Waters of Texas A&M. As we described in an article about his research last spring, he’s not afraid to rewrite history. Waters contacted Gustafson about performing new tests on the rib with the bone point.

Waters modern tests confirmed Gustafson’s suspicions. New radiocarbon dates confirmed that the site was 13,800 years old. High resolution CT scanning and three-dimensional modeling confirmed that the embedded bone was a spear point, and DNA and bone protein analysis showed that the bone point was made of—get this—mastodon bone.

“The evidence from the site shows that people were hunting mastodons with bone weapons before the Clovis stone spear point,” says Waters.

In addition, the new evidence supports extinction theories of large mammals at the end of the last Ice Age. During the last cold period, herds of mammoth, mastodon, camels, horses and other animals roamed Texas and North America. At the end of the Ice Age, these animals became extinct.

“While these animals were stressed by the changing climate and vegetation patterns at the end of the Ice Age, it is now clear from sites like [this one] that humans were also hunting these animals and may have been a factor in their demise,” Waters adds.

Timing is indeed everything. The current research was published last week in the journal Science.

Image courtesy of Center for the Study of the First Americans, Texas A&M University

Catching glimpses into our fossil ancestors’ daily lives is a tricky business. Fossil remains of our ancestors can only tell us so much concrete information, and tracing our DNA backwards in time can only get us so far.

But bones and teeth hold more clues than you’d think, if you just know how to extract them. In a new research paper published in the journal Nature, evolutionary anthropologists harnessed cutting-edge chemical tools and analyses to uncover the social patterns of our earliest ancestors and in so doing, discovered that males weren’t too keen on leaving their childhood homes.

The study, led by Sandi Copeland of the Max Planck Institute for Evolutionary Anthropology, looked at fossilized teeth from South Africa: eight Australopithecus africanus (2.2 million years ago) individuals and 11 individuals belonging to the Paranthropus robustus (1.8 million years ago) species. Using a laser, the team extracted a key element from the tooth enamel called strontium.

The strontium found in tooth enamel is like a snapshot into where the person lived during childhood, when permanent teeth developed. The various types of strontium, called isotopes, can be connected with specific geographical regions. “The strontium isotope ratios are a direct reflection of the foods these hominids ate, which in turn are a reflection of the local geology,” Copeland explains.

The research team divided sets of teeth for both species into male and female based on size (male teeth are generally larger). They then performed strontium isotope analysis on each, looking for clues into the each specimen’s childhood geographical landscape. They found that a large majority of male specimens – nearly 90% – grew up in the same general area where the fossilized teeth were uncovered. They were born, grew up, and died in pretty much the same place: the prehistoric equivalent of their hometown.

But analysis of female strontium isotopes revealed a different history. Over 50% of female remains trace to further afield, away from the dolomite cave systems that so many males grew up near. It seems that many females spent their formative years elsewhere, only arriving in the area once they reached adulthood.

Chimpanzees, our closest living primate relatives, exhibit a similar social structure. Male chimps are highly territorial, and will not leave their home base, even upon reaching adulthood. To prevent inbreeding, females are often forced to leave their childhood groups in search of new mating partners in other groups. Copeland’s strontium-isotope analysis lends support to the idea that early hominids might have done the same. If this structure exists in both chimpanzees and early hominids, perhaps its origins extend much further back in time.

“One of our goals was to try to find out something about early hominin landscape use. Here we have the first direct glimpse into the geographic movements of early hominids,” says Copeland.

The study not only provides insight into previously unknown aspects of ancient hominin social structure, it also highlights exactly how much new information can be squeezed out of a fossil specimen. As Julia Lee-Thorp, one of the study’s co-authors, explains, “Studies like these really bring home that finding and describing fossils is not the end of the story. Thoughtful application of these new analytical methods can tell us such a lot more about the details and lives of the distant past.”

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Image: Darryl de Ruiter

There’s been much to say over the past few years about the possibility of significant interactions – and even interbreeding – between early members of our species, Homo sapiens, and our evolutionary cousins, Neanderthals. But now, new analysis of Neanderthal remains from western Russia casts doubt on the notion that we coexisted at all. Instead, the Neanderthals of western Russia appear to have died out before we even arrived. Results of this study were reported in last week’s online edition of the Proceedings of the National Academy of Sciences.

The research team, led by archaeologist Ron Pinhasi of University College Cork, questioned the analysis of two Neanderthal infants excavated over 10 years ago. The infants were found in the Mezmaiskaya Cave near the Caucasus Mountains of western Russia. Using carbon-14 dating, along with traditional stratigraphic methods (comparing ages of surrounding sediment layers), these infants were originally dated to about 30,000 years ago, just when humans were making their way into the region. This led many to wonder whether the two species ever came into contact, and to what extent.

But Pinahsi and his team were unconvinced the dating techniques were accurate. Central to their skepticism was the fact that the layers of sediment between which the infants were found were themselves dated incorrectly, skewing the original results.

But archaeological dating techniques have improved vastly over the past decade. So Pinhasi and his team put these new techniques to the test, by reanalyzing the Neanderthal infant remains directly. Specifically, Pinhasi harnessed the expertise of Thomas Hingham of Oxford University. Hingham has developed a new method of filtering samples that removes contaminants such as dirt, leaves, and collagen recovered from bone. This can give a far more accurate radiocarbon reading.

According to Hingham, “Previously, research teams provided younger dates which we now know are not robust, possibly because the fossil has become contaminated with modern particles. This latest dating evidences sheds further light on the extinction dates for Neanderthals in this key region.”

When putting the infant bone samples through the filter and dating them again, they found the infants to be 39,000 year old—9,000 years older than previously thought.

These infant remains had been strong evidence that humans and Neanderthals could have interacted with each other in western Russia. Now it is clear they were dead 9,000 years before humans showed up. Could this same story play out in other parts of the Europe and Asia?

“It now seems much clearer that Neanderthals and anatomically modern humans did not co-exist in the Caucasus, and it is possible that this scenario is also true for most regions of Europe,” says Pinhasi. He points to many instances of problematic dates for other archaeological sites excavated over the past several decades.

The western plains of Russia, like the Near East, were a prehistoric crossroads for early humans and our fossil ancestors. The revised analysis of the Mezmaiskaya Cave infants highlights the vast uncertainties we still hold surrounding the early expansions of our species, and our interactions with Neanderthals. But it also opens the door to new discoveries.

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Image: Luna04/Wikimedia