Recent genetic studies, however, support Sarich and Wilson’s early work. The complete human genome was published in 2004, and the chimp genome followed in 2005. That year, scientists at Arizona State University and Pennsylvania State University compared modern human mitochondrial, or maternal, DNA with chimpanzee, macaque and mouse DNA to determine the point at which each lineage diverged from our common ancestor. “Though we will never know the exact date of the split, we can estimate that date using differences in their DNA,” explains Blair Hedges, an evolutionary biologist at Penn State. These differences, or mutations, are assumed to occur at a constant rate, which can be used to estimate how much time has passed since lineages diverged. This method, called the molecular clock, indicated that the human and chimp lineages split five million to seven million years ago, although more fossil-based research is needed to confirm that idea.
Advances in genetic testing are also answering long-standing questions about Homo neanderthalensis, better known as Neanderthals. Modern humans and Neanderthals coexisted 30,000 years ago, and many anthropologists have wondered whether the two species ever mated. In 1997, scientists at the University of Munich in Germany extracted the first Neanderthal DNA from an upper-arm-bone fossil found in 1856. Several years later, researchers at Lawrence Berkeley National Laboratory and the Joint Genome Institute, operated by the University of California, partially sequenced the Neanderthal genome, which allowed scientists to look for Neanderthal-specific sequences in modern human mitochondrial DNA. The results showed that Neanderthals were 99.5 percent genetically identical to modern humans. “But the Neanderthal sequences for this gene do not show any equivalent to current modern human populations,” says Ludovic
Orlando, an assistant professor at the École Normale Supérieure in France, who has also worked with Neanderthal DNA. Although it’s possible that Neanderthal sequences could have been weeded out of our genome over time, the research strongly suggests that the two species never mated.
Some of the most exciting molecular research in anthropology today focuses on ancient human migration. African populations possess the greatest diversity of genetic mutations, which supports fossil evidence that the human lineage began there. But what happened next? Scientists are looking at genetic mutations in isolated populations around the world to answer that question. In the coming years, this data, coupled with the fossil record—Dart’s Taung child included—will help confirm what routes modern humans took out of Africa 100,000 years ago.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.