THE BIOLOGY BOOK
Oldest DNA and Human Evolution
Svante Pääbo (b. 1955)
In December 2013, the world’s oldest evidence of human development was discovered, a finding that raised a number of evolutionary questions. A femur (thigh bone) fossil was recovered from the “pit of bones,” an underground cave in northern Spain, from which scientists had recovered twenty-eight nearly complete human skeletons since the 1970s. From the powdered femur, Matthias Meyer and his colleagues at the Max Planck Institute in Leipzig, Germany, extracted mitochondrial DNA (mtDNA) that dated back some 400,000 years, 300,000 years older than the previous humanoid DNA sample.
Upon preliminary examination, the anatomy of the femur resembled a Neanderthal, but a comparison of the DNA evidence showed a much closer relationship to the Denisovans, whose DNA had been previously analyzed from 80,000-year-old remains found in Siberia, 4,000 miles to the east. This finding challenged the narrative of human development based on previously discovered fossil remains and DNA analysis. Humans, Neanderthals, and Denisovans were generally believed to have had a common ancestor in Africa some 500,000 years ago. This ancestor diverged from humans, left Africa, and split once again, 300,000 years ago, into the Neanderthals and Denisovans. The Neanderthals traveled west, toward Europe, and the Denisovans, east. Our human ancestor remained in Africa, giving rise to Homo sapiens, who 60,000 years ago migrated to Europe and Asia, where they interbred with the Neanderthals and Denisovans, who became extinct. But the new DNA evidence raises the question: Why are Denisovan fossil remains in Spain?
The new DNA findings were only made possible because of advances in retrieving ancient DNA. When a biological organism dies, its DNA breaks down into small fragments, which in time mix and become contaminated with DNA from other species—in particular, soil bacteria. In 1997, Svante Pääbo, a Swedish biologist specializing in evolutionary genetics, also working at the Max Planck Institute, discovered a new technique for retrieving DNA fragments, which he used to determine the genome sequence of the Neanderthal in 2010 and the femur in Spain. It is possible that advances such as this may rewrite our biological history.
SEE ALSO: Neanderthals (c. 350,000 BCE), Anatomically Modern Humans (c. 200,000 BCE), Lucy (1974), Genomics (1986), Mitochondrial Eve (1987), Human Genome Project (2003).
The jaws of Homo heidelbergensis, an extinct species that lived in Europe, Africa, and western Asia possibly as far back as 1.3 million years ago. It was the first human species to live in colder climates and may have been the first to bury its dead.