Evolution Study Tightens Human-Chimp Connection

January 24, 2006
Chimpanzee
Georgia Tech scientists found that the rate of molecular evolution of chimpanzees is closer to that of humans than it is to other apes.

Scientists at the Georgia Institute of Technology have found genetic evidence that seems to support a controversial hypothesis that humans and chimpanzees may be more closely related to each other than chimps are to the other two species of great apes – gorillas and orangutans. They also found that humans evolved at a slower rate than apes.

Appearing in the January 23, 2006 issue of the Proceedings of the National Academy of Sciences, biologist Soojin Yi reports that the rate of human and chimp molecular evolution – changes that occur over time at the genetic level – is much slower than that of gorillas and orangutans, with the evolution of humans being the slowest of all.

As species branch off along evolutionary lines, important genetic traits, like the rate of molecular evolution also begin to diverge. They found that the speed of this molecular clock in humans and chimps is so similar, it suggests that certain human-specific traits, like generation time, began to evolve one million years ago - very recently in terms of evolution. The amount of time between parents and offspring is longer in humans than apes. Since a long generation time is closely correlated with the evolution of a big brain, it also suggests that developmental changes specific to humans may also have evolved very recently.

In a large-scale genetic analysis of approximately 63 million base pairs of DNA, the scientists studied the rate at which the base pairs that define the differences between species were incorrectly paired due to errors in the genetic encoding process, an occurrence known as substitution.

“For the first time, we’ve shown that the difference in the rate of molecular evolution between humans and chimpanzees is very small, but significant, suggesting that the evolution of human-specific life history traits is very recent,” said Yi.

Most biologists believe that humans and chimpanzees had a common ancestor before the evolutionary lines diverged about 5-7 million years ago. According to the analysis, one million years ago the molecular clock in the line that became modern humans began to slow down. Today, the human molecular clock is only 3 percent slower than the molecular clock of the chimp, while it has slowed down 11 percent from the gorilla’s molecular clock.

This slow down in the molecular clock correlates with a longer generation time because substitutions need to be passed to the next generation in order to have any lasting effect on the species,

"A long generation time is an important trait that separates humans from their evolutionary relatives,” said Navin Elango, graduate student in the School of Biology and first author of the research paper. “We used to think that apes shared one generation time, but that’s not true. There’s a lot more variation. In our study, we found that the chimpanzee’s generation time is a lot closer to that of humans than it is to other apes.”

The results also confirm that there is very little difference in the alignable regions of the human and chimp genomes. Taken together, the study’s findings suggest that humans and chimps are more closely related to each other than the chimps are to the other great apes.

"I think we can say that this study provides further support for the hypothesis that humans and chimpanzees should be in one genus, rather than two different genus’ because we not only share extremely similar genomes, we share similar generation time,” said Yi.

Even though the 63 million base pairs they studied is a large sample, it’s still a small part of the genome, Yi said. “If we look at the whole genome, maybe it’s a different story, but there is evidence in the fossil record that this change in generation time occurred very recently, so the genetic evidence and the fossil data seem to fit together quite well so far.”

Source: Georgia Institute of Technology

Explore further: Virtual reality helps make sense of complex scientific data

Related Stories

Virtual reality helps make sense of complex scientific data

July 30, 2015

Virtual reality (VR) is a billion-dollar industry familiar to gamers but recently VR technology has been used to make sense of the enormous scientific dataset that is the Avon Longitudinal Study of Parent and Children (ALSPAC).

Why we should welcome 'killer robots', not ban them

July 30, 2015

The open letter signed by more than 12,000 prominent people calling for a ban on artificially intelligent killer robots, connected to arguments for a UN ban on the same, is misguided and perhaps even reckless.

How a single molecule turns one immune cell into another

July 30, 2015

All it takes is one molecule to reprogram an antibody-producing B cell into a scavenging macrophage. This transformation is possible, new evidence shows, because the molecule (C/EBPa, a transcription factor) "short-circuits" ...

Recommended for you

How bees naturally vaccinate their babies

July 31, 2015

When it comes to vaccinating their babies, bees don't have a choice—they naturally immunize their offspring against specific diseases found in their environments. And now for the first time, scientists have discovered how ...

A cataclysmic event of a certain age

July 27, 2015

At the end of the Pleistocene period, approximately 12,800 years ago—give or take a few centuries—a cosmic impact triggered an abrupt cooling episode that earth scientists refer to as the Younger Dryas.

New blow for 'supersymmetry' physics theory

July 27, 2015

In a new blow for the futuristic "supersymmetry" theory of the universe's basic anatomy, experts reported fresh evidence Monday of subatomic activity consistent with the mainstream Standard Model of particle physics.

Dense star clusters shown to be binary black hole factories

July 29, 2015

The coalescence of two black holes—a very violent and exotic event—is one of the most sought-after observations of modern astronomy. But, as these mergers emit no light of any kind, finding such elusive events has been ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.