Nested Biological Hierarchies

You must not read the same articles I do, then. With the sequencing of the chimp genome the differences and similarities are coming ever more precisely known - and we share many, many genes that are totally inactivated, particularly in our odod-sensing systems. Many of them are still active in, say, Old World Monkeys who still rely more on smell than we (great apes) do. I think that the recently reported lower percentages of similarity are due to the fact that slightly different measures of the difference are being used. Can one of you biologists clarify?In whatever case, we are more closely related/have more similar DNA to chimps + bonobos than to anything else alive. Our DNA is more similar to chimp DNA than that of the house mouse. Mus musculus, is to another member of that genus, Mus spretus. It wouldn't spell out things as clearly as it does here in the real world, where they just keep digging up fossils of proto-whales and not-quite-modern-human primates, and keep finding genes that anatomically related groups like artiodactyls and primates share within group to the exclusion of other groups. "Nested hierarchy," they call it.

Read what I wrote again, Nem: I'm not even referring to the relatedness of mice and men (to coin a phrase). I'm saying that M. domesticus and M. spretus, two mice, have less similarity in their DNA (based, however, on just 12,000 genes or so) than do Homo sapiens and Pan paniscus.Enard, et al., Science, 296, 340-343, (2002).

Which is why Linneaus initially put humans and chimps together in the genus Homo.

In addition to the GLO gene, there is a urate oxidase pseudogene that has the same "break" in great apes but not monkeys. We and chimps can't oxidize uric acid because of this, so we can get gout - but it may help us live longer, as uric acid is an antioxidant. We share at least dozens of pseudogenes for odorant receptor proteins with various primates, as well. I'd have to look up the particulars, but the more visually-oriented primates, particularly those with three-color vision, seem to have developed sight to the exclusion of being able to smell as many things as a lemur. Same for the vomeronasal organ of great apes and humans - we don't even keep the organ past the fetal stage, so we don't keep many of the genes for its receptors.

Based on the primate critters that all share that particular break in the GLO gene, it's real probable that the critter that we inherited the break from was a tree-dwelling monkey-ish sort of animal that ate a lot of fruit. The same animals that have the GLO pseudogene tend to have pretty good color vision, to see when fruit are getting ripe and full of vitamin C. And humans living close to the land didn't seem to have that much trouble with vitamin C deficiency - sailors used to get scurvy before they took fruit along to eat, but landlubbers typically get berries or other fruit now and again. (Though city-dwellers in the impoverished Third World may be in the same boat, so to speak, as the pre-Limey sailors were.)Anyway, we humans got that broken gene from an ancestor that ate a lot of fruit, and for whom the lack of vitamin C synthesis was no handicap. We're kind of stuck with it, as there have been enough random mutations in it since the "break" that the chances of it regaining function through mutation are pretty durn slim. The screamingly obvious signs of our relatedness, again, are in the things we share that are "broken." We have a bunch of pseudogenes related to smell sensors in common with great apes - and they are functional genes in other primates. We have broken urate oxidase genes - same pattern. Humans and great apes start growing a vomeronasal organ and its "receiver", the accessory olfactory bulb of the brain as fetuses, but reabsorb the bulb and nearly lose the VNO by the end of infancy. Most other primates keep these bits as social/sexual sense organs.And all this stuff fits into those nested hierarchies.....