“We’re so closely related genetically, yet our behavior is so different. This [study] will allow us to look for the genetic basis of what makes modern humans different from both bonobos and chimpanzees.” — Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The Beginnings of Genetic Similarities
In 2012, an international team of researchers sequenced the genome of the bonobo. They found that it, like the chimpansee, shared around 99 percent of its DNA with humans. The team also found small differences in the genomes of the three species that could explain why chimps and bonobos don’t look or act like humans.
Closest Living Relatives: the Chimps
Back in 2005, researchers had sequenced the chimpansee genome and discovered that it was our closest living relative.
The discovery of the bonobo’s close relationship with humans has prompted scientists to speculate about the ancestor of chimpansees, bonobos and humans. They wonder if it looked like a chimp or bonobo or something else. They also want to know more about the evolution of all three species. Ancestral humans split off from ancient chimps and bonobos between 4 and 7 million years ago. Chimpansees and bonobos split off from each other about one million years ago. They are still very closely related and share about 99.6 percent of their DNA.
Genetic ties between chimpansee, human, and bonobo
The research team at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany found that humans and bonobos shared 1.6 percent of their DNA with each other, but not with the chimpansee. Similarly, they found that humans and chimpansees shared 1.6 percent of their DNA with each other, but not with bonobos. That points to a large and genetically diverse population of ancestral apes with perhaps 27,000 reproductive active adults.
Scientists have also been learning why humans, chimps and bonobos are so different despite having over 98 percent of their DNA in common. Part of the reason is simply due to the numbers of genes involved. Each human cell has three billion base pairs in it, and 1.2 percent of that equals 35 million base pairs. (Base pairs, which are always bonded pairs adenine and thymine or ctyosine and guanine, join together to form the DNA double helix.)
In addition, even identical genes can work differently. Gene activity or expression can be turned up or down like the volume on a radio. Chimpansees and humans have many of the same genes regulating their brains, but the human genes are more active which is why humans have bigger and smarter brains than do chimpansees. In fact, geneticists have identified a gene that stimulates development of the cortex in both chimps and humans, and they have also found that humans have an extra copy of the gene. They believe that humans gained that extra copy after their family tree diverged from that of chimpansees.
Chimpansees Nurturing Genetics
The genetic similarities and differences between humans, chimpanzees, and bonobos can be seen in their reproduction, nurturing and mothering. Hence nurturing genetics. For example, studies show that all three primates have gestations lasting nine months, and all three usually have single offspring that are born helpless. In all three species, the young take years to reach adulthood and need nurturing genetics to survive. Chimpansee mothers, like their human counterparts, protect and nurture their babies and are primed to do by their nurturing genetics.
On the other hand, baby chimpansees usually develop their first teeth between the ages of three to five months, while a human infant usually doesn’t start teething until they’re around six months. While chimpansees generally mature faster than do humans, they paradoxically nurse for a longer time. Their nurturing genetics seem to be more central in their lives. A chimpansee may continue to nurse until it’s five years old, and its mother will also gather food for it. After the chimp turns five though, the mother stops feeding it or letting it nurse, as the youngster is now old enough to get its own food.
Just as girls might play house, chimps begin making sleep nests like their mothers when they’re around six months old. So both young humans and chimps both learn by imitating adult behaviors.
These shared nurturing genetics contribute to the fact that chimpansees are indeed our closest living relatives.