Oh and just to stick to the topic of this blog...
Everything in life is a trade off.
posted by Mad Scientist @ 5:52 PM
I'm a virologist working hard to prevent the spread of HIV through research and education. Please visit the AVERT prevention site linked below and feel free to ask any questions here.
7 Comments:
but these are both comparatively new diseases in humans, right? so how could such tradeoffs be already in place?
Well that depends on if you look at things from the host (human) or viral view. Ok I'm going to talk evolution, but think about it in the context of a human lifetime, not where did people come from.
We humans have many receptors that can do the same thing. There are two co-receptors for HIV. In the context of humans we don't have these receptors around for the virus we have them around for other reasons. Somewhere somehow 1% of the population lost one of the co-receptors. People can live without this receptor because of redundancy (this is not true of ALL receptors, but for the majority of them). Why did humans lose this gene? Who knows, but it had nothing to do with the viruses.
Now think on the level of the virus. Viruses replicate much faster than humans therefore evolution is sped up. HIV evolves to use two coreceptors (R5 and X4) R5 (the one mentioned in the article) is found on almost all immune cells in the body of all people so this is an excellent choice (umm not choice but selective pressure) for the virus to make. The virus doesn't know or care if 1% of the population will be immune to it. Westnile again probably adapted in some way to exist in human hosts. The virus replicates and mathmatically the more replication the more chance of mutation. mutation is evolution.
There are all kinds of math models out there that are above my head, but I bet if you did the statistics for any receptor, protein or enzyme in the human body you would find that it lends some protection against certain pathogens and creates a disadvantage against others. Not because Humans evolved that way, but because the pathogens evolve to exist in humans.
Certainly if you put some bacteria on a petri dish with all the essentials it needs and let it grow there are few selective pressures involved, but introduce that same bacteria into a host organism or even different compartments of a host organism and the selective pressures for survival change dramatically.
As Rosanne RosannaDanna said, it's always something.
I like your idea about studying lizard & starfish genes to figure how humans could grow new limbs. And I never realized that sharks don't get cancer. Do other sea creatures?
Scat- Well sharks don't get solid tumors. I'm not sure about other forms of cancer. As I have to devote most of my time to what pays the bills I am behind on my shark trivia. I believe other sea creatures are susceptible. Sharks are just so darn cool they are prehistoric so they must have good genes to not have become extinct in all these eons. I started college studying marine biology, but quickly realised the job market was limited and science took me in a different direction, but I am still fascinated by the ocean.
Wasn't there a fad (maybe still ongoing) about people snorking down shark cartilage because they think it will prevent cancer? Sounds dubious at best.
Goodness, Mad, we don't care that you're too busy finding ways to save millions of lives, we want another blog entry! :-)
yes, Mike there was (or maybe is) to the point where some shark species were endangered, thus putting thousands of documentary makers out of work...
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