Sunday, 9 December 2007

Junk In The Trunk

Our genes are full of germs. This is a good thing.

Junk DNA outnumbers useful DNA in every cell in our bodies four to one. Over our evolution we have picked up billions of pieces of genetic information which does nothing for DNA's main job: building the proteins which hold us together. Where did the trash come from?
Viruses, like HIV, have existed in myriad forms throughout evolutionary history. They are nothing on their own -- they can barely be called 'life' -- so need a host in order to survive and photocopy themselves. Some of these viruses had the ability to infect the sex cells, and affected a sperm or egg in a small enough way that the offspring survived. The virus moved in and became part of the genetic code, passed on in perpetuity.
Jared Diamond's book,"Guns, Germs, and Steel" makes the point that all epidemics through recorded history originated in animals. Diseases that were harmless to, say, chickens or monkeys became transmittable to humans and took our system unawares, as we had no established defense. Did you know that gorillas can't get AIDS? If you were to inject a gorilla with HIV, its body would fight it in 80 different ways. In a chimp, 130 ways. You see, after parting ways on the evolutionary tree, the higher apes contracted a virus that humans did not: the PtERV virus. Because viruses evolve one thousand times faster than the systems they are attacking, gorillas (or at least the ones that survived) carry genetic material from 80 variations of that virus. This genetic information may have been useless for a long time, but if a gorilla was in a Sudanese ghetto it would be breathing pretty easy right now.
The irony is that a previous virus (TRIM5a) protected pre-humans from PtERV. Now we don't get PtERV to protect us from HIV.
We've got all this genetic baggage that we carry around, and every so often it comes in useful. It's junk in our trunk. It shows where we've been, what battles we've fought, what we're prepared for. Scientists are fossicking through the human genome and reviving these long-dead viruses to look for clues about how to fight current diseases. (This isn't as tough as it sounds; a team of biologists was able to make a polio virus from materials available via mail-order.)
HIV/AIDS is the main focus in applied virus research. There are many reasons for hope, the first of which is that our species has faced many, many deadly viruses in the past, as evidenced by our genetic burden. Another is that viruses reproducing is like Homer Simpson building robots: most of them don't work, and even fewer can make copies of themselves.

For more information, here's a link to a New Yorker article. (It's about 5000 words.)


Michael said...

If a gorilla was in a sudanese ghetto, it would be pretty anxious I would say, even if it was having sex with African men or women . And lets be honest, who wants to have sex with a gorilla? What is the gorilla going to do, force itself upon them, just to exercise its genetic superiority when it comes to aids? And where is a gorilla going to get $5? Robbery? Gorillas by nature are not aggressive animals. Perhaps then by selling his paws or genitals, which will ironically not only prevent him from "not getting aids in 80 ways" but will also end up as an aprhrodeisiac, encouraging the very promiscuous behaviour the gorilla had come to sowetto to no doubt prevent? For what other reason would a gorilla come to the dangerous, overpopulated streets of sowetto, than to spread the message of safe sex? As a social animal, it is well within the normal behaviour of a gorilla to behave in ways to protect his pack and we can be sure that a gorilla, who lives on roots, shoots and leaves, would not come to sowetto, with its flat breads, beans and maize, unless he felt some kind of kindred spirit with mankind

Really, a bit of editorial commonsense wouldnt go astray, Mr Longbourne.

Logan Longbourne said...

You're quite right. I should have made clear that I do not believe that HIV can be transmitted by close contact (unlike Presidential candidate Mike Huckabee). Nor am I suggesting that gorillas visit poor African nations trolling for hookers. I challenge the assumption, however, that the higher apes are ambassadors of safe sex, as they themselves engage in real and simulated sex without regard to gender for reasons of dominance. If humans did this, all sporting matches would be on the Playboy Channel.
As a service to our readers, please note that SOWETO is 3500km from the nearest point in SUDAN. But who cares, because they're both basically fucked.