In a common evolutionary trunk, it is known that the orangutan is our cousin thrice removed, the gorilla is our cousin twice removed and the chimp is our first cousin (with which we share 96 % of our genetic information). A new research led by an international team from North Carolina State University, University of Aarhus in Denmark and the University of Oxford in Britain found that chimpanzees and humans split off from a common ancestor just 4 million years ago, much later than the current hypotheses, that state for 5 to 7 million years ago.
The research team compared DNA patches of humans and all big apes, man’s closest relatives: the chimpanzee, the gorilla, and the orangutan. The researchers employed for the first time in this type of study a well-known type of statistical calculation, named the hidden Markov model which was developed in the 1960s and till now used only to speech recognition, reaching this different result about human differentiation. “Assuming orangutan divergence 18 million years ago, speciation time of human and chimpanzee is consistently around 4 million years ago. Primate evolution is a central topic in biology, and much information can be obtained from DNA sequence data,” said Dr. Asger Hobolth of North Carolina State University.
Each species has a molecular clock recording the speed at which DNA mutations occur. The speed may not be constant, but over large periods of time it evens, so in millennia the average is constant. The team focused on four DNA zones of the human, chimpanzee and gorilla. The results disagree with other investigations, showing that in just 400,000 years the human lineage split off from the common chimp-human ancestor. In May 2006, David Reich of the Broad Institute at the Massachusetts Institute of Technology and Harvard Medical School’s Department of Genetics got similar results for the splitting age (4 million years), but his team finally chose a 5.4 million years old for the divergence.
Reich’s genetic analysis research rose the hypothesis that the early human ancestors and the chimp’s ancestors could have interbred freely long after their separation. Another 2006 research made at the Georgia Institute of Technology discovered genetic evidence that, in fact, chimpanzees are closer to humans than to gorillas and orangutans. The molecular clock revealed that humans evolved one unique feature just a million years ago: our longer lifespan and our longer childhood, humans maturing sexually extremely late compared to apes.
