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It's not 2.5B T. Rex at the same time. 2.5 billion Tyrannosaurus rex lived and died during the roughly 2.4 million years I'm in a meeting so I'm not totally p
by tessierashpool 6y ago
It's not 2.5B T. Rex at the same time.
2.5 billion Tyrannosaurus rex lived and died during the roughly 2.4 million years
I'm in a meeting so I'm not totally paying attenion to this comment as I write it (sorry) but I believe that works out to just a little over 1000 per year. That's not a huge number for an entire species across an entire planet.
- deleted 6y ago[deleted]
- sanj 6y agoDeeper in the article, there's an estimate of a 19 year lifespan. So ~20k alive at any point in time, assuming a flat distribution during that 2.5B year window.
- chrisco255 6y ago20k seems unlikely low, even as a median. A population that small would be difficult to sustain for that long through variations in climate, resources, ecosystem, and evolutionary competition.
- kelnos 6y agoThey need not have been spread across the entire planet, though. 20k in a smaller area might have been fine.
- dharmab 6y agoThere is a supported theory that at one point there were 10,000 or fewer humans on the planet: https://en.wikipedia.org/wiki/Toba_catastrophe_theory#Genetic_bottleneck_in_humans https://en.wikipedia.org/wiki/Toba_catastrophe_theory#Geneti...
- chrisco255 6y agoThis claim is not that there was 20K T-rexes at one dire point in history but an average over millions of years. Humans ended up surviving that disaster, and then went on to populate the whole earth. Also side note, supervolcanoes are scary as hell.
- antisthenes 6y agoOn the contrary, for apex predators, smaller populations are easier to sustain than large populations. Especially apex predators of that size.
- chrisco255 6y agoYeah but the prey was even bigger. Have you seen brontos? Everything was bigger in that era, including plants and trees.
- antisthenes 6y agoNot sure what your comment has to do with mine. That doesn't mean the total available biomass to predators in aggregate was larger or smaller, just because some big dinosaurs existed. It doesn't even mean T-rex hunted brontosaurus frequently or at all (given the somewhat different eras), much like the modern lions don't really hunt adult elephants.
- midasuni 6y agoT Rex lifespan of what, 10-20 years? That’s a tiny number - about 3 TRexes in the entire country of Belgium
- deleted 6y ago[deleted]
- jimmy2020 6y agosounds a boring meeting.
- kjeetgill 6y agoIt's worth pointing out to anyone in the comments before they read the article: They arrived at the ~20k number living at any one time number first; ~1k per year * 19yr lifespans. They extrapolated it out to that 2.5B based on how long they were around. Parent reverse engineered it in reverse!
- teachingassist 6y agoIt seems extremely unlikely that there was a flat population for millions of years (considering e.g. the human population has doubled in the last 50 years), and this wouldn't be my starting assumption. A small, flat population is even more unlikely - any disruption would wipe out the population more quickly than millions of years down the line.
- AlotOfReading 6y agoPopulations reach equilibrium very quickly on a geologic timescale. Humans had a relatively flat population graph until the past 10kya or so as well (and realistically long after that point as well).
- jjk166 6y agoYou have to have a flat population over long timescales. If you started with two tyrannosaurs and had a population growth rate of just 0.02% (population doubles every 6600 years), there would be approximately 500 billion tyrannosaurs on the planet at the same time by the point they went extinct. It's likely the population fluctuated up and down slightly on short timescales, but the average would have been constant. They were spread out over a continent so any disruption would need to be very widespread to take them all out - which eventually of course is exactly what happened. Humans are unique in that we can develop technology to exceed our carrying capacity.
- neolog 6y agohttps://en.wikipedia.org/wiki/Estimates_of_historical_world_population#/media/File:Population_curve.svg https://en.wikipedia.org/wiki/Estimates_of_historical_world_...
- Impossible 6y agoWhen I first saw the headline I imagined flocks for T-Rexes devouring everything. 2.5B for all of history is more reasonable
- Sharlin 6y agoThey were not spread across the entire planet, though, far from it. They lived in what is now Western North America and used to be an island continent called Laramidia[1]. [1] https://en.wikipedia.org/wiki/Laramidia https://en.wikipedia.org/wiki/Laramidia
- pbreit 6y agoIn that case then "2.4m years" is the unbelievable number.
- maldeh 6y agoI'm frankly astonished that the species lasted for two and a half million years all while being highly endangered the whole time. Like, nevermind a comet, a poorly timed burp from a volcano could have sufficiently reduced diaspora enough to make them disappear.
- creamynebula 6y agoOne of the threads that make me wish we had downvotes here... Very deceiving clickbaity title!
- DiggyJohnson 6y ago> I'm in a meeting so I'm not totally paying attention to this comment I'm in a meeting too and your comment made me chuckle. I love the idea of HN-goers going through the motions of professional life, when in reality they just want to talk about dinosaurs and the nuance behind dinosaur research.
- text70 6y agoYou think that is fun, you should get some biotech friends. We actually talk about what it would take to recreate Jurassic park in real life.