How Close Are We?

Fossil records suggest that long ago, well over one hundred species in forty genera of apes existed in the tropical forest canopies across Africa, Asia, and southern Europe. Most died off slowly without leaving any descendants. Many factors may have influenced great ape evolution, including environmental change: the contraction of forests, the emergence of predators, and the appearance of competing species. Scientists consider anatomic similarities and fossil evidence, and, more recently, have used comparative DNA testing as a sort of molecular clock to establish distinct evolutionary lineages and their timeframes.

Orangutans, the least terrestrial of the surviving great apes, were the first lineage to split from the common ancestor of the African great apes (gorillas, humans, chimpanzees and bonobos) some fifteen to nineteen million years ago. The remaining cleavages from the family tree appeared relatively close together. The predecessor of the modern-day gorilla separated from the line and the common ancestor of humans, chimpanzees, and bonobos nine to eleven million years ago. The human ancestor was next to leave the line, approximately five to eight million years ago, with the chimpanzees and bonobos the last to separate, as recently as 800,000 to 2.6 million years ago.

Chimpanzees and bonobos are our closest living relatives, sharing an astonishing 98.4 percent of our DNA. Gorillas and orangutans follow closely behind, with 97.7 percent and 96.4 percent similarity in DNA respectively. This surprising “closeness” recently enabled scientists studying malaria—the disease that has caused the most human deaths in all of history—to uncover the molecular explanation for how the parasite jumped from gorillas to humans. They made their discovery by examining a fifty-thousand-year-old gene segment of gorilla DNA that we humans share.

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