Here's a snippet of ur-biotech history:

The first edition of On the Origin of Species, by Charles Darwin, was published in 1859. The following year its author presented his theory of evolution to a large and distinguished audience in London. Thomas Huxley, an eminent British biologist, introduced and championed the speaker. At the end of Darwin's presentation, the Bishop of Oxford, Samuel Wilberforce (1805-1873) asked bitingly, "I beg to know, is it through his grandfather or his grandmother that Huxley claims his descent from a monkey?" To which Huxley muttered, "The Lord hath delivered him into my hands." And then answered, "If there were an ancestor whom I should feel shame in recalling it would rather be a man, endowed with great ability and a splendid position, who should use these gifts to obscure the truth."

A century or so later, phylogeneticists determined that the chimpanzee (Pan troglodytes), the closest relative to humans (Homo sapiens) had diverged some 5 million years ago.

In 1968, a group of scientists, among them biophysicist Roy Britten at the Carnegie Institute of Washington, published an educated estimate that chimps and humans were within 98.5 percent of homologous identity. "I didn't do the original chimp estimate," Britten allowed. "Other people did. All I did was develop the hydroxyapatite technique. We needed that in order to study the whole problem of the repeated DNA sequences."

Britten explained the hydroxyapatite technique: "You know what happens when you heat DNA. It separates the two strands. You can repair them by incubating them with enough salt present, then they will get back together again. If you happen to have mixed labeled DNAs from one species with an unlabeled majority from another, then the labeled pairs will all be interspecies. Then by melting those strands and measuring them, you can get an idea of the stability and the percent match. Hydroxyapatite," he continued, "is just a way of collecting double strands and separating them from single strands. Then when you heat it, they melt and continuous strands come off.

"There had always been an interest in the evolutionary relationship of primates and people," Britten recalled, "and this was a way of getting a molecular estimate of it. We didn't develop 98.5 percent for that purpose. It just came along. We wanted to study repeated sequences in DNA. That was what I discovered."

How Interspecies Closeness Got New Measure

"Over the years since the 1960s, this 98.5 percent has achieved a kind of currency that people quoted and cited. Dozens and dozens of books," Britten recalled, "said we were close to chimps, by 98.5 percent similar. They made big issues about it, but 98.5 doesn't make us any more similar.

"I've done a lot of sequencing," he recounted. "I simply took their sequences from GenBank. They have not made these comparisons, and when I started them I had no idea that this insertion-deletion - indel - difference would turn up. I was just looking to check the old values."

Britten is senior research associate emeritus at California Institute of Technology. He is sole author of a paper in the Proceedings of the National Academy of Sciences (PNAS) titled: "Divergence between samples of chimpanzee and human DNA sequences is 5%, counting indels." In other words, the decades-old evolutionary gap of 98.5 percent has suddenly spread to 95 percent He wrote a special Fortran computer program to compare nearly 780,000 base pairs of the human genome with a similar number from the chimp genome.

"This revised estimate," Britten told BioWorld Today, "supplies a new technique for comparison of species. Since we haven't known very similar species, DNA has not been compared on this scale of long stretches. So we haven't known there were a lot of indels - that is, insertion-deletion DNA stretches. Their comparisons to a lot of gene agents will just add a new way of sequence analysis, and probably won't change any of the species relationships.

"Indels," Britten explained, "are just places where DNA is missing from one species and present in the other, as seen in the DNA double-helix alignment. Easiest to align are homopolymers. The bulk of these identical radicals are different in length between chimps and humans, by 80 percent, in fact. Homopolymers are DNA, mostly poly A. And what happens is that during replication, slippage occurs, so the length of the region changes. They just increased divergence. If you're going to go and line up human and chimp DNA and see how much of it is identical, that is the idea here. If you run across some piece that's missing, you can't count it. You have to count it as missing. That just changed the fraction of the DNA which actually matched, so reduced it to 95 percent."

Britten now plans "to go and see if the genes are exactly what I expect them to be, which is free of indels. If I find any by chance that are different in the gene region, of course, everybody will be interested because that's important in looking at the real inter-species evolution. New data will arrive when the full sequence of Pan troglodytes is complete. It's been okayed, money is available, and it might happen in a year."

Dark Clouds On Special-Interest Horizon

"In the early days," Britten recalled, "people thought that the orangutan was our closest neighbor, and found it wasn't so. But since you couldn't tell chimps from gorillas, they were both close. And it took those hydroxyapatite measurements to make the first break in that, by hemoglobin comparisons. It's still not quite proved. I didn't change anything in the chimp-human relationship. It's merely a different measure and a new one," he added, "but makes no difference; it just points to the interesting way in which evolution occurs.

"I knew what would happen as soon as the media picked up this story," Britten recounted. "One of the reporters who talked with me about the change seriously raised the issue that it will cause trouble in animal rights, because people will say Hey, it's not so close!' It will have that kind of use and it's sort of annoying," he concluded, "but there it is."