Re: [evol-psych] The human immune system may limit future evolution
- On Tue, 2 Jul 2002 16:18, Ian Pitchford quoted:
> Dr George suggests that the limited number of functional genes in theThis does not follow, since it ignores the fact that there isn't a
> human genome may be a result of the presence of a more advanced
> immune system. The immune system is designed to protect us from
> disease, but it is important that the cells of the immune system do
> not recognise our own tissues or cells, as this would lead autoimmune
> Autoimmune disease is avoided by killing off any immune cells that
> recognise molecules produced by the body (self-molecules). This means
> that the larger the genome, the more self-molecules the immune system
> needs to tolerate.
> As a result, the immune system has to kill more immune cells. If
> there are too many genes then this results in the vast majority of
> immune cells dying, paralysing the immune system, and leaving the
> body unable to fight off disease or infection.
fixed number of immune cells in the body, nor do all they all have to
be produced at once.
Effectively the immune system can be considered (in part) a production
line for producing a certain number of immune cells. Immune cells that
recognise self-molecules are rejects, immune cells that don't are
While efficiency is important, you can still produce a healthy immune
system with a 50% reject rate, or even 99% or higher. It will just take
longer and be more wasteful. Since the immune system does not produce
cells entirely at random, it isn't clear to me that a high failure rate
would even be significantly more wasteful.
There is a good test of Dr George's hypothesis. Are there any species
with functioning immune systems with significantly more genes than we