Fossil hints that Jurassic mammals lived slow and died old | Hacker News Reader

Fossil hints that Jurassic mammals lived slow and died old

nytimes.com

105 pointsPetiver19 comments

I wonder if the harsh post impact environment selected for small, short lived creatures due to the lower caloric energy requirements, and faster genetic iteration speed respectively. If your environment is particularly hostile with low resources then taking many small bets quickly might be the favored play.

It would be interesting to know what the climate was too. If these animals hibernated or slowed their metabolism during cold periods it would help explain their longevity.

Scotland was around 35 degrees latitude and the Jurassic period was fairly warm compared to now (tropical plants are found up to 60 degrees latitude) so it’s unlikely there was a winter to hibernate through.

However there was significantly more oxygen in the atmosphere back then. There could be a metabolic component related to that since absorbing O2 was probably easier.

We have no idea when that transition happened, though, and if it is related to the impact. The time from when these animals lived in the Jurassic to the impact at the end of the Cretaceous is considerably longer than the time from the impact until today, much could have happened inbewteen.

It seems logical that a faster Metabolism, quicker to reach reproductive viability organism would frequently outcompete slower variants In the same biome niche.

Not really, since a faster metabolism requires more energy upkeep, and food scarcity has always been one of the biggest selection criteria in nature.

Frequently.

Eh, no, that qualifier does not fix your argument, because it's not a caveat. Natural selection by definition works on which trait outcompetes the other one most frequently, it's a statistical process.

There is a reason life works on a sigmoid growth curve and not an exponential growth one.

I think maybe people thought I was asserting that it was generally a better solution… I was not.

But fast reproduction is hardly a rare trait in nature. An ideal solution would be variable rate metabolism, and we see that in species capable of hibernation. Of course slow metabolisms have advantages in resource constrained environments.

Metabolically slow ambush predators (some snakes, spiders, etc) can also do extremely well in a given niche, and some of these strategies are ancient.

Frequently.

the predominant theory is that the length of an organism's lifespan is inverse to the rate of it's metabolism. Look into Kleiber's law. Also worth reading the book Scale by Geoffrey West.

Thanks for the recommendation.

There are also advantages to being slower. Check out https://en.wikipedia.org/wiki/R%2FK_selection_theory , which I reference historically and encompasses also the discussion on Wikipedia about subsequent refinements of the theory.

Mammals were the startups of the Jurassic era ( just survive and you might end up being huge later )

Is it possible due to the more oxygen rich environment during the jurassic era?

“Fossils”

Yeah, I was reading it as the VCS for a moment there.

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