Angry in the Great White North

From the Independent:

They are man's closest cousins and they are staring into the abyss. But in one of the most important environmental treaties, hope has been offered to stop the headlong slide towards extinction of humankind's nearest relatives, the great apes.

I wonder, though, if anyone has thought of the possible downside of a large and thriving simian population.

I'm thinking the potential of new diseases being cooked up in the bloodstreams of these animals, the mutation rate getting higher and higher as more and more individual animals are around to act as hosts.

Recall that everything about viruses depends on the specific genetics of the host:

All viruses reproduce by taking over the reproductive mechanism of a host cell, so the first thing a virus must do is get into a cell by passing through the cell's membrane. They do this by means of their receptor-binding protein. These proteins are encoded in the viruses' genetic material and they stick out from the surface of the virion. They are attached either to the capsid or part of the envelope, depending on the type of virus. These proteins cause the virion to bind to specific receptors on the host cell in a manner similar to the way a key fits into a lock. This interaction between the host cell's receptor and the virus' receptor-binding protein is crucial and causes the "specificity of infection". This specificity usually limits a viruses' infection to specific types of cells and specific animals (or plants or bacteria) depending on the virus.

For example, HIV (the virus that causes AIDS) has receptor-binding proteins that attach to specific types of human white blood cells. Because of its specific receptor-binding protein, HIV cannot infect skin cells or lung cells so it is not infectious by touch or by breathing it in. In addition, HIV does not infect monkeys because the receptors on monkey cells are not the right shape to accept HIV's receptor-binding protein. However, a related virus, called SIV, can infect monkey cells because it has evolved a receptor-binding protein that attaches to monkey white blood cell receptors.

This is unlike bacteria (like the bubonic plague) and parasites (like malaria), which work on a much higher level of organization and so routinely move from species to species.

So on one level, fewer close relatives to humans is a good thing. Fewer reservoirs of potential viral infections to jump the species gap. It sounds horrible to say, but maybe it's a good thing we're the only hominids on the planet, and that our contact with pongids, hylobates, and other simians is so limited. Even as it is, it is likely they gave us HIV (see this report from the BBC, hat tip to David Goldberg).

Swine flue and chicken flu? Terrible. But think of the millions of contacts taking place all over the planet every single day. For all that, the occurrence of cross-species viral infection is exceedingly rare. Think of how much "bushmeat" (monkey and ape) is consumed. Result: HIV/AIDS.