The End is at 2 o'clock

June 6, 2004 2:27 PM

Size does matter. The size of your species' telomeres. Reinhard Stindl proposed a new theory for extinction -- the internal clock model. "It could explain the disappearance of a seemingly successful species, like Neanderthal man, with no need for external factors such as climate change."
posted by raaka (9 comments total)

Wow, very interesting. The idea that a species as a whole 'ages' in a manner similar to an individual is pretty wild. Does anyone know why inbreeding would cause telomeres to lengthen? Seems like it would exacerbate whatever potential for disaster was already present in the genepool...
posted by crank at 2:46 PM on June 6, 2004

Absolutely fascinating. If this turns out to be true it would change so many things .. it would be like a real live paradigm shift. It will take a while to prove but the theory does have a certain beauty that species have a set lifespan just like individuals.
posted by stbalbach at 3:17 PM on June 6, 2004

I've heard of this before. Simple evidence against it, from a friend who works in genetics:

Sharks (and other species) which don't exhibit any of the problems supposedly asociated with ancient species, e.g. sharks get virtually no cancers.

Fathering of children by older men should reduce the life expectancy of thier offspring (as the male gametes are produced close to time of use) - there is no evidence for this

posted by daveg at 4:14 PM on June 6, 2004

Playing devil's advocate for daveg: It could just be that sharks have developed strong anti-neoplastic immune systems; fathering of children by older men are more likely to have genetic defects that those by younger men.
posted by gramcracker at 4:57 PM on June 6, 2004

the old fathers having more genetic defects is just due to breakage and point mutations that occur with so many cell divisions, i've never heard anything about it having to do with telomeres. i would assume telomerase is active in the testes. embryos (human) do have active telomerase, which is a enzyme that extends telomeres. also many neoplastic cells have extremely active telomerase, and when you probe for telomeres in tumors they are often abnormally long. this is thought to be a reason tumors can undergo so much cell division while normal cells cannot.

So, telomeres are a very simple gene sequence that is repeated over and over, in humans it is only TTAGGG over and over. I find it highly doubtful that a species would go extinct due to an inability to upregulate a gene that they already have, and it seems near-impossible that this is the cause of >90% of all extinctions, meaning no type of organism could find a way to turn on a gene that 1. they have already and 2. has been on previously in their lives.

It is almost certainly due to some misunderstanding on the part of the guardian, but this sorta sounds like the group-selection, for-the-greater-good sort of idea that people like to inject in to natural selection. selection works for the individual only, not for the family, and certainly not for the whole ecosystem. yes photosynthesis made our atmosphere oxygen rich, which helped other things evolve, but not at a cost to the phytoplankton, they were acting in their own best interest. It is not in the best interest of a species to go extinct, and i can't see why it would be so hard to stop telomere degradation if it were the reason.
posted by rhyax at 7:21 PM on June 6, 2004

Yeah and it seems to me that the vast majority of extinctions aren't mysterious - they were just out-competed.
posted by kavasa at 7:26 PM on June 6, 2004

About Neaderthals, not too long ago, among the limited number of Neaderthal skulls that exist, someone noticed a protrusion into the sinus cavity in two or three of the skulls.
The purpose of this protrusion might be to slow down air as it is inhaled, which would be very good during an ice age, as the air would warm up before entering the trachea.
Unfortunately, when the ice age was over, and the world became warmer and moister, this would condemn them to a lifelong sinus infection. Which could have wiped them out.

And while natural selection was mentioned, there was no mention of mutation theory. When a true superior mutant is born, if it is not destroyed by its progenitor species, its offspring supplant their progenitors with astonishing speed.

A theory that could be applied to humans. If a superior species of human were to be born and propagate, it would quickly supplant us. Nothing personal, mind you.
posted by kablam at 8:29 PM on June 6, 2004

That process may be currently underway :

Homo Urbanis.

They are everywhere.
posted by troutfishing at 4:44 AM on June 7, 2004

So. That'll be an excuse to start cloning then.
The team's data shows that the telomeres are actually getting longer in each generation of clones. "If you look back at the paper on (the six-generation clone) mice in Nature (Wakayama et al., 2000), they're showing the same trend," Cibelli said.
posted by seanyboy at 6:14 AM on June 7, 2004