A cranium found in 1972 and the lower jaw of a newly discovered fossil,
shown reconstructed and combined above, are believed to be from
the same ancient hominid species.
The big-brained, upright primates of the genus Homo—the group to which we modern-day humans belong—evolved in East Africa around 2.4 million years ago. By half a million years later, Homo erectus, from whom we’re directly descended, was walking the plains near Lake Turkana in what is now Kenya. But anthropologists have increasingly come to believe that Homo erectus wasn’t the only hominid around. Three newly discovered fossils, detailed online this week in Nature, confirm that at least two other Homo species lived nearby—providing the strongest evidence yet that several evolutionary lineages split off in the genus’s early days.
Over the past few years, several studies have illuminated some of what happened during the brief period when modern humans and Neanderthals overlapped in Europe, with genetic analyses showing that the two groups interbred tens of thousands of years ago (though not frequently) and ancient remains suggesting that modern humans fought and—more controversially—ate their prominent-browed contemporaries.
It seems that humans and Neanderthals made occasional love and intermittent war, but what were those interludes of interaction actually like? What was going on inside those distinctive crania? It’s a tricky question to answer—behavior doesn’t fossilize—but anthropologist Thomas Wynn and psychologist Frederick L. Coolidge combine genetic and anthropological evidence with a healthy dose of well-informed speculation to offer an intriguing picture of how Neanderthals may have lived, thought, felt, and acted.
Could Neanderthal DNA have protected our ancestors from diseases?
What’s the News: While we humans have certainly outlasted our hominin cousins, new research shows that Neanderthal and Denisovan genes may have helped us spread far and wide. By mating with the two species, our ancestors acquired genes that allowed them to adapt to diseases outside of Africa far quicker than would have been otherwise possible, according to Peter Parham, a professor of microbiology and immunology at Stanford University.
What’s the News: Archeologists have discovered thousands of stone tools in Texas that are over 15,000 years old. The find is important because it is over 2,000 years older than the so-called Clovis culture, which had previously thought to be the first human culture in North America. As Texas A&M University anthropologist Michael Waters says, “This is almost like a baseball bat to the side of the head of the archaeological community to wake up and say, ‘hey, there are pre-Clovis people here, that we have to stop quibbling and we need to develop a new model for peopling of the Americas’.”
How the Heck:
What’s the Context:
Not So Fast:
The Future Holds: Now it’s time for archeologists to rethink the North American narrative of migration: How did humans first populate the continent? As James Adovasio, the executive director of the Mercyhurst Archaeological Institute, told NPR, “Everything we’re learning now, from genetics, from linguistic data, from geological data, from archaeological data, suggests that the peopling process is infinitely more complicated than we might have imagined 50 years ago, or even 20 years ago.”
Reference: The Buttermilk Creek Complex and the Origins of Clovis at the Debra L. Friedkin Site, Texas. By Michael R. Waters et al. DOI: 10.1126/science.331.6024.1512
Image: Courtesy of Michael R. Waters
Neanderthals: They weren’t really into distance running. According to research by David Raichlen in the Journal of Human Evolution, they were more the power walking type: The shape of a Homo sapiens heel compared to that of a Neanderthal would have allowed our ancestors to be much more efficient runners over long distances.
Raichlen stated with living humans, studying them as they ran on treadmills.
By looking at MRI scans of their ankles, he found that the distance between a point on the heel bone just below the ankle bone, and the back of the heel bone where the Achilles tendon attaches, was proportional to the runner’s efficiency. The shorter this distance, the greater is the force applied to stretch the tendon – and the more energy is stored in it. This means that people with shorter distances are more efficient runners, using less energy to run for longer. [New Scientist]
With this knowledge, Raichlen and colleagues looked at the remains of Neanderthals as well as humans of the same era. The difference, he says, was distinct.
Though attempts to teach creationism (or its twin sister, intelligent design) in the classroom have been struck down in court, these anti-science approaches still influence the teaching of evolution in American schools. Barely more than one-quarter of 926 high school science teachers who responded to a survey published in Science this week unabashedly taught evolution in their classrooms.
Michael Berkman and Eric Plutzer of Penn State have been watching this story for years, tracking whether courtroom victories like 2005′s Kitzmiller v. Dover Area School District truly freed up teachers to teach evolution without fear. In an early 2008 study, a book, and new results published in Science, the answer is a depressing “no”:
Only 28% of the 926 teachers surveyed, “unabashedly introduce evidence that evolution has occurred and craft lesson plans so that evolution is a theme that unifies disparate topics in biology.” … Most biology teachers belong to the “cautious 60%,” who are “neither strong advocates for evolutionary biology nor explicit endorsers of nonscientific alternatives,” the study says. [USA Today]
It’s not that a wave of creationism is overtaking our biology teachers—just 13 percent of respondents said they advocated that viewpoint. What’s more likely, Berkman and Plutzer say, is a crisis of confidence. Says Berkman:
“The survey left space for [the teachers] to share their experiences. That’s where we picked up a lot of a sense about how they play to the test and tell students they can figure it out for themselves. Our general sense is they lack the knowledge and confidence to go in there and teach evolution, which makes them risk-averse.” [LiveScience]
Early humans trekking out of Africa moved faster than we thought they did: New archeological evidence suggests they reached the Persian Gulf 50,000 years before we previously thought.
Archeologists excavating a rock shelter in Jebel Faya, in the United Arab Emirates, found a cache of hand axes and other tools that date back 125,000 years ago. Their age was established by dating the silicon in the chert tools, and also via comparison to other artifacts:
Team member Anthony Marks of Southern Methodist University, an anthropologist, said the tools were made in ways consistent with the 125,000-years-ago time period and therefore raise the inevitable question of how they got to the area near the Persian Gulf…. “Either these people came out of East Africa or they came from nowhere,” he said. [The Washington Post]
The team’s research, published in Science, posits that the area’s climate had a role in spurring mankind’s expansion around the planet. Climate records suggest that the Red Sea was much shallower during an ice age that lasted from 200,000 to 130,000 years ago, because much of the world’s water was trapped in glaciers. This allowed early humans to cross the now-shallow Red Sea for new land in the southern Arabian peninsula, the researchers say. After the crossing, these early humans would have found themselves in a surprisingly fertile place: Towards the end of that ice age, the deserts of Arabia experienced a brief “wet” era with rivers, lakes, vegetation, and wildlife.
Welcome to the family of critters with sequenced genomes, orangutans. In Nature this week, scientists unveil the draft DNA sequencing of our great ape cousins—the only great apes that live exclusively in Asia.
The researchers assembled the draft genome of the female Sumatran orangutan (Pongo abelii) using a whole-genome “shotgun” strategy, an old-fashioned approach that cost about $20 million. In addition, the researchers gathered sequence data from five wild Sumatran orangutans and five Bornean orangutans (Pongo pygmaeus) using a faster and thousandfold cheaper next-generation platform. [LiveScience]
What did scientists find in there? For one thing, orangutans share about 97 percent of the their genome with humans, compared to the 99 percent we famously share with chimpanzees. The two orangutan species—inhabiting the Indonesian islands of Borneo and Sumatra—diverged about 400,000 years ago, lead author Devin Locke says. That’s much more recently than scientists had thought.
They also discovered that over the last 15 million years, orangutan DNA changed at a different rate than either ours or chimps’. Orangutans have undergone fewer mutations of the DNA, have a lower gene turnover rate, and have fewer duplicated DNA segments.
Diet, brains, murder at the hands of a certain species called Homo sapiens, life expectancy: These and more have been floated as reasons to explain the vexing question: Why did Neanderthals die out about 30,000 years ago while our ancestors persisted?
In a study in this week’s Proceedings of the National Academy of Sciences, Erik Trinkaus argues that we should scratch the last one—life expectancy—off the list. His wide-ranging survey of Neanderthal and early human remains shows that our ancestors had no particular advantage over the Neanderthals in living into old age.
Dr. Trinkaus studied fossil records of humans from across Eurasia and of Neanderthals from the western half of Eurasia to estimate adult mortality in the two groups. He found that there was approximately the same number of adults in the 20-to-40 age range and over-40 age range in both groups. [The New York Times]
Putting on clothing to protect our woefully hair-deficient bodies is one of the key moments in the history of becoming human. Just when our species took this step, however, is open to a fair amount of guesswork—scientists can’t exactly dig up fossilized parkas and trousers. But what scientists can do is determine roughly when two species diverged, and that has made all the difference: Using the lice that have traveled with people for thousands of years, a team has tracked the time that humans first became dedicated followers of fashion—perhaps as long as 170,000 years ago.
The key to the study by David Reed and colleagues, which appears in Molecular Biology And Evolution, is that there are two kinds of lice that hang around humans: the head lice that live on our scalp, and the body lice that live in our clothes. At one point in the past these two shared a common ancestor, Reed reasoned, and the body lice would have split off and become a separate group once they had human clothing in which to live.
So if we can figure out when they arrived at the scene, we’d have a minimum age on clothes. Thanks to modern molecular techniques, we can compare the genomes of these two lice and come up with that date. For the curious, a “Bayesian coalescent modeling approach” tells us that we were going clothed at least 83,000 years ago, and maybe as far back as 170,000 years. [Ars Technica]