Humans And Chimpanzees, How Similar Are We?

November 28, 2006

The DNA sequences of humans and chimpanzees are 98.5 percent

identical, but now Uppsala University researchers can show that

parts of the genetic material are missing in one species or the

other. This means in some cases that humans can produce a protein

that the chimpanzee lacks and vice versa. The study, being published

in the November issue of the Journal of Molecular Evolution,

estimates that the total variation between humans and chimpanzees is

rather 6-7 percent.

The chimpanzee, together with the pygmy chimpanzee (the bonobo), is

the closest relative to humans still in existence. Even though the

similarities between chimpanzees and human are obvious, there are

clear differences in body structure, intellect, and behavior, etc.

In the more than five million years that have passed since the

developmental lines of humans and chimpanzees parted, mutations have

altered the genes. A key issue for researchers studying the

evolutionary history of humans and chimpanzees is to understand

which of these differences have been crucial to the development of

the species and their unique characteristics.

Tomas Bergström and his research team at the Department of Genetics

and Pathology have compared the DNA sequence from chromosome 21 in

humans and chimpanzees to map where the genetic differences are

found and what significance this might have. The findings

corroborate other studies that indicate that in 1.5 percent of the

genetic material a nucleotide (genetic letter) has been replaced by

another nucleotide. But the findings also show that more than 5

percent of the genetic material occurs in only one of the species.

In both species, DNA has been added or lost. In other words, the

total difference is estimated at 6.5 percent. Even though most of

the differences occur, as expected, in parts of the genetic material

that do not contain genes, the research team has found that pieces

of DNA have been added or lost in 13 percent of the genes. Some

genes (5 percent) have undergone such major changes that certain

proteins can probably not be produced by one of the species.

" It is probable that a species can compensate for this by producing

a similar protein from another part of the gene, but some of these

differences have clearly been crucial to the development of the

species, " says Tomas Bergström.

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