In reference to the well-known Christian story of Adam and Eve, many scientists specializing in evolutionary history refer to the oldest known member of a species as its “Adam”. It is expected that the human “Adam” lived about 200,000 years ago, and that the gorilla “Adam” lived about 100,000 years ago. Gorillas have a much smaller Y chromosome genetic tree than humans which reflects the society of gorillas being structured as an alpha male society. It is well known that humans are closely related to apes, and many think that the gorilla is actually our closest living relative. The truth behind the genetic tree history are that chimpanzees are the species that we most likely evolved from, being as their “Adam” has been recently discovered to have been older than originally thought. Genetic trees of chimpanzees show a very deep ancestry in their Y chromosomes which lead scientists to believe that the chimpanzee “Adam” is over 5 times as ancient as the human “Adam”. The chimpanzee “Adam” is expected to have lived over 1 million years ago, as determined based on the research completed by the University of Leicester.
Professor Mark Jobling from University of Leicester’s Department of Genetics led a team of geneticists that published their research study in the Journal of Genome Research. This team determined DNA sequences of a large part of the Y chromosome. They did this because the Y chromosome is exclusively passed from fathers to sons which allows for the determination of the species’ “Adam” by tracing back as far as possible in the species’ male history. The experiment also interpreted patterns in the mitochondrial DNA passed from the mothers to the offspring. These sets of information allowed for the team to construct genealogical trees (family trees) to compare species and subspecies. The experiment was done with 19 great ape males, 19 chimpanzees, 4 bonobos, 14 gorillas and 6 orangutans. The analysis revealed that to estimate the time between common ancestors they needed to compare mitochondrial DNA based phylogenetic trees. The comparisons between these phylogenies emphasize the human diversity from other relative species and reiterate that specific branch lengths reflect differences in long term generations.
Image from Wikimedia Commons
Connections in their experiment and between the crafted genealogical trees by the University led to the discovery of the chimpanzee version of “Adam” living approximately a million years ago. The depth of the chimpanzee Y chromosome history suggests that female and male chimpanzees mate with each other indiscriminately. Even considering this, the Y chromosome and mitochondrial DNA trees show humans looking much more similar to gorillas than chimpanzees. This is because unlike the chimpanzees indiscriminate mating, both humans and gorillas did not and do not practice a free-for-all choice of mating. This means a few males have access to most of the females and many males do not have access at all. This suggests that our evolutionary history is closer to the gorilla mating system than the chimpanzees even though the chimpanzee origin is much more ancient than our own.
- “Ancient Chimpanzee ‘Adam’ Lived over One Million Years Ago, Research Reveals.” — University of Leicester. Universty of Leicester, 25 Feb. 2016. Web. 25 Feb. 2016.
- “Great-ape Y-Chromosome and Mitochondrial DNA Phylogenies Reflect Sub-species Structure and Patterns of Mating and Dispersal.” Genome Research. Cold Spring Harbor Laboratory Press, 16 Feb. 2016. Web. 25 Feb. 2016.