A long-standing debate was reignited this month by Morris Goodman and colleagues at the Wayne State University in Detroit, who claim that humans and chimpanzees “are so alike at the level of their DNA that they should both be classified as members of the human genus Homo” (The Independent).

This controversial idea is not new. In 1991, Jared Diamond at the University of California dubbed humans “the third chimpanzee” and last year, Simon Easteal at the Australian National University agreed that this “makes sense; they are very similar to us, in genetic terms” (The Age).

Previous estimates of the genetic similarity between humans and chimpanzees have ranged from 95–98.5%, but Goodman's figure of 99.4%, based on functional sequences, is the highest yet.

The new analysis also indicates that the two lineages split only 5–6 million years ago, which Goodman believes is strong support for his case and “should dictate whether they belong within the same genus” (New Scientist).

Criticism of this research — “the figure that you get depends on precisely which genetic differences you look at” (BBC News) — has been welcomed by Goodman, who hopes that the discussion will prompt a symposium to “determine if this is a reasonable proposal” (USA Today).

But “would it make a real difference if chimpanzees were members of the genus Homo rather than Pan?” (The Guardian). It would seem so, as the ethical and legal implications range from “the use of chimps in laboratory experiments ... (to) their conservation in the wild” (New Scientist) — with this issue “a small change in classification translates into a big one in moral attitudes” (The Guardian).