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

As slight as these finds are, scientists know quite a bit about these ancient hominins. In 2010, a team of scientists isolated and sequenced DNA from that finger bone fragment and discovered that it belonged to a young girl of an extinct Homo species described as Denisovan—after the Denisova cave in Siberia where the remains were found.

Unfortunately, the sequencing wasn’t reliable enough to do further studies. ScienceNOW explains:

But these genomes were too low quality to produce a reliable catalog of differences. Part of the problem was that ancient DNA is fragmentary, and most of it breaks down into single strands after it is extracted from bone.

Enter Matthias Meyer, a postdoc from Germany who developed a new way of sequencing. His novel technique splits the DNA double helix so that each of its two strands can be used for sequencing. This allowed the same team of scientists to sequence every position in the Denisovan genome about 30 times over ensuring that each nucleotide was in the correct spot.

The technique provides 99.9% accuracy—a quality similar to genomes that have been determined from present-day humans!

The much-improved genome furthers our understanding of the 50,000 year-old individual and population. The young girl had brown hair, eyes and skin and the genetic variation of Denisovans was extremely low—suggesting their population was never very large for long periods of time.

In addition, studies of the genome enhance our comprehension of human evolution. They describe the divergence between Denisovans and modern-day humans and confirm that modern populations from the islands of southeastern Asia (like Papua New Guinea) share genes with the Denisovans.

“This research will help determine how it was that modern human populations came to expand dramatically in size as well as cultural complexity while archaic humans eventually dwindled in numbers and became physically extinct,” says study co-author Svante Pääbo.

The findings were published last week in Science.

Image: Max Planck Institute for Evolutionary Anthropology

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

Hominid fossils always make big news, and the interest extends to older primate fossils as well. Remember the big media splash Ida made at the announcement of her discovery? The European Darwinius masillae fossil, touted as the missing link in primate evolution back in 2009, had a book deal, documentary, and website. All for one fossil!

Primates are divided into two categories: lemurs and anthropoids (monkeys, apes, and humans). Ida, at 47 million years old, seems to lie at the beginning of the branch for anthropoids. Despite looking lemur-ish, Ida was missing a grooming claw: anthropoids have nothing but toenails and fingernails, while lemurs have a distinctive grooming claw.

At the time, dissention broke out in the scientific ranks, with many people arguing that too much hoopla had erupted over one fossil—and that Ida may be a “link” in human evolution, but not the “missing” one.

Well, last week, scientists published an article about Ida’s North American cousin, Notharctus tenebrosus (also 47 million years old).  While studying its fossil, researchers discovered an odd-shaped second toe. It has claw-like features near the base, but the tip is more flat, much like a modern monkey nail.

So what kind of link is Notharctus? Where does it fit in the family tree? Good question, says a new article about the fossil in PLoS One.

Study co-author Doug Boyer of Brooklyn College says the primate was “either in the process of evolving a nail and becoming more like humans, apes and monkeys, or in the process of evolving a more lemur-like claw.”

He also questions the origin of both nails and claws in the primate family tree. “I now believe it’s more likely that nails were the starting point and grooming claws developed as a functional trait.”

Lead author Stephanie Maiolino of Stony Brook University is unsure that claws and nails are even that significant. “It’s not clear that lacking a grooming claw means a species is related to anthropoids.” Take that, Ida!

One of the authors of the Ida study has already expressed disagreement with some of the findings of this current study. We can expect more to come on this lemur-anthropoid battle… Nature might be “red in tooth and claw,” but we hope the paleoanthropologists will settle this nail-biting mystery without much violence.

Image: PLoS One

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

Exciting announcements about human evolution have captured our attention recently. First, we added a new branch to our family tree with Ardipithecus ramidus, or “Ardi.” Then we learned our earliest primate ancestors may have evolved not in Africa (contrary to conventional wisdom) but in Asia.  And now, fossil remains from China seem to radically change what we thought we knew about our species’ arrival in East Asia. It’s been a busy year for human evolution, and the year’s not over yet.

In the most recent discovery, published last week in the Proceedings of the National Academy of Sciences, an international team of experts described three fossils: two teeth and part of a jaw. The remains were found in Zhiren Cave in southern China. They date back 100,000 years, and the authors say the fossils are of human origin.

This discovery has ruffled a few feathers among the experts. Why? Because conventional wisdom places the arrival of humans into East Asia just 50,000 years ago. The remains from Zhiren Cave are twice as old.

Both fossil and genetic evidence place the origin of humans in Africa about 150,000 years ago. According to conventional widsom, humans didn’t make the long trek to Asia for another 100,000 years. Once they got there, most experts agree, they pushed out or replaced the groups of earlier ancestors, like Homo erectus, who had been living there for over a million years.

The discovery of these fossils may change that timeline. Erik Trinkaus from Washington University in St. Louis (and one of the paper’s authors) noted, “These fossils are helping to redefine our perceptions of modern human emergence in eastern Eurasia, and across the Old World.”

What makes these fossils so interesting isn’t just their age, the authors say. It’s the fact that they have a mix of human and archaic (you might say “pre-human”) features. The chin especially is decidedly human (our earlier ancestors were chin-impaired), while other features seem much more primitive. Are these remains the result of humans and Homo erectus “intermingling”?

This discovery does not come without its critics, however. John Hawks from the University of Wisconsin questions whether the presence of a chin alongside archaic features is a convincing enough argument. With so few remains, he says, we need to know how genes build the jaw in the first place before we can understand how these remains fit into the twigs and branches of our family tree.

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

“It’s important that scientists disagree. We’re trained to be skeptical, to be critical, “ according to the Academy’s own Peter Roopnarine, PhD, Curator of Invertebrate Zoology and Geology. “It’s actually when they agree that it’s significant. And there’s overwhelming agreement in the scientific community about global warming.”

In fact, according to this New York Times article, “nearly 90 percent of some 3,000 climatologists who responded agreed that there was evidence of human-driven climate change, 80 percent of all earth scientists and 64 percent of meteorologists agreed with the statement.” (What’s up with meteorologists? Find out here.)

Climate deniers may argue that scientists don’t agree on the science behind global warming, but overall, they do.  As seen in so-called “Climategate,” the arguments within the emails weren’t about the science, but about how to proceed with the findings and how to communicate the details. As published earlier this week, the science discussed in the emails was reviewed by other scientists and found to be sound, to be true.

Let the scientists disagree about the South African hominid skull. As Dr. Roopnarine points out, it wouldn’t be such a big deal if we were talking about an ancient clam.

But Earth? And humanity’s future on it? That is a big deal. And when it comes to climate change, scientists find plenty to agree on.