Some days ago there was news about some researchers predicting mammals would be doomed by the next supercontinent cycle, due to too high temperatures incompatible with warm blooded creatures. Well, if mammals can just evolve back cold blood, perhaps that makes their thesis moot. See https://hackertimes.com/item?id=37654289
Mammals have adapted to adverse conditions before. However, the current rate of change is unprecedented. Evolution does not happen in one or two generations.
This prediction isn't about climate change, it's about the formation of a new super continent. Because it'll be such a large landmass, and the energy from the sun increases by about 1% every 100 million years, the inner parts of this continent are predicted to be too hot to support most life as we currently know it. Of course, who can really say what will happen / evolve / be there by that time anyway?
In a catastrophic climate change scenario Humans generally don't die because of heat, but because other humans throw bombs at them to get at their farmland.
There there were a lot of scientists in the 70s and 80s predicting collapse of food production, who weren’t slightly wrong but spectacularly wrong.
The last few decades has seen an exponential reduction in poverty, and the largest increase of food production in human history (It’s a statistical fact). To predict that will suddenly reverse is a heck of a bold claim.
I'll take that any day over 2km thick ice cover. The closes homo sapiens ever got to extinction was 120k years ago during the last ice age.
Is changing climate a challenge? Of course it is, for every living being that got used to the status quo. Being desperate about it is the opposite of what we want to do as desperation leads to stupid decisions (geoengineering, rapid one sided deindustrialisation etc).
In that scenario, humans with barely enough farmland to feed themselves are going to trade food against non-edible crops. Then the traders will be bombed by the humans now starving because their food was taken away, and you have the same situation except more local.
Good luck trading for enough food when your former high yield farmland only allows for light goat herding or poverty crops now because the glaciers that you relied on are no longer there and your aquifers are empty.
In the last couple of years I've been thinking more often about a Venus scenario where life does not survive. We are just hoping that life will find a new equilibrium in the next couple million years like it has in the past. But if temperatures rise too fast, the planet will just get cooked before enough CO2 will be sequestered. The great filter is still in front of us.
I mean, we have bacteria living off of the heat and gases of underwater volcanoes — it is absolutely not realistic to think that life itself will be in jeopardy. It has survived the release of a highly reactive gas that killed off the majority of things (oxygen), a huge meteor that introduced a huge cooldown overnight, etc.
Of course, it doesn’t mean that we should not try to stop the impending doom that will kill off an insane amount of species, and render many populous places unlivable for humans, causing famine and wars - but Life itself will never be in any danger.
The Venus is quite a lot closer to the Sun, though. A few degrees C change in the average temperature of the Earth indeed can cause absolute large changes, potentially killing of most more complex life forms, but even that would be very far off from the point where life is infeasible - especially that the bottom of the ocean won’t be reaching anywhere close to temperatures where proteins denaturate.
Venus gets roughly double the sunlight that earth does, also:
“Conditions possibly favourable for life on Venus have been identified at its cloud layers, with recent research having found indicative, but not convincing, evidence of life on the planet.” https://en.wikipedia.org/wiki/Venus
I've sometimes wondered if Venus' runaway greenhouse had been caused (presumably unintentionally) by intelligent Venusians in the distant past, how could we find out? What bio- or techno-signatures would we still be able to find? And what possible such signatures would be easiest to look for given the inhospitable conditions?
We have a long, long way to go before Earth could be considered hot by historical standards. The IPCC worst-case warming scenario, where we do absolutely nothing to curtail global warming, puts us back at the midpoint in 2100.
Our 4.54-billion-year-old planet probably experienced its hottest temperatures in its earliest days, when it was still colliding with other rocky debris (planetesimals) careening around the solar system. The heat of these collisions would have kept Earth molten, with top-of-the-atmosphere temperatures upward of 3,600° Fahrenheit.
The second source is a chart going back 500 million years.
How is that related to IPCC projections and climate change, which are about the environment humans evolved to survive and thrive in - physiologically over 7 million years (when we had the last common ancestor with chimps), culturally and technologically over 10 thousand years.
I’m responding to the comments about the extinction of life on Earth, not the extinction of humanity. As you can see on the graph, for most of the last 500 million years the Earth was hotter than it is now, and obviously there was life.
I was not referencing the first couple paragraphs of the linked article, since obviously the first few million years of Earth’s existence are irrelevant, and they’re the same source, which tells me you did not actually read the article; please read through next time and respond charitably rather than assuming I’m some kind of crank. I would appreciate it if you read to understand rather than to respond. It’s very frustrating when people replying to you assume you are saying something completely different rather than reading what you said within its context - a Venus scenario wiping out all life. HN commenters should do much better. This isn’t Reddit. Your entire comment is premised on me saying or thinking something I never suggested or implied.
It’s true that humanity has survived during hotter and colder periods, but certainly nothing like that depicted on the 500mil graph, and anyway industrial civilization is obviously much more fragile.
> In the last couple of years I've been thinking more often about a Venus scenario where life does not survive. We are just hoping that life will find a new equilibrium in the next couple million years like it has in the past. But if temperatures rise too fast, the planet will just get cooked before enough CO2 will be sequestered. The great filter is still in front of us.
Clearly, even a rapid return to the projected IPCCC 2100 worst-case numbers will not cause this scenario. Would it be deleterious for advanced industrial civilization? [1] Yes. Would it continue to be part of the mass extinctions we're causing? Yes. Will it "cook the earth" or "boil the oceans" as he suggests downthread? No.
[1] And so are a lot of other things. Whether people like it or not, advanced industrial civilization is unsustainable with or without climate change.
Yes, there are annual plants that evolve significant adaptations to avoid water loss within five generations (5 years), in response to drought. Things like having smaller flowers, flowering earlier in the spring, and smaller leaves. Many plants also have a lot of phenoplasticity that allows them to adapt without genetic (evolutionary) change.
That argument is only true for humans and other "long" lived species. For example look at at how much canines have evolved in the same time span that homosapiens have stayed relatively "static".
Long and static, in very very relative terms, of course.
If you mean dogs — they were bred by humans for that purpose, that operates very distinctly from “raw” evolution.
The latter is not particularly fast at adopting, it survives mostly by having a huge variety in the first place, and in an adverse environment some will survive, quickly growing in numbers due to the abundance of resources left behind by other former competitors. But that only works if the adversity is not too extreme, at least in case of more complex life forms (plants, animals).
Does that mean it can’t? I know at least a few people who are especially sensitive to heat and cold. It seems likely there are folks out there who could continue to survive environmental changes given our population, just not as many as currently exist.
Or in fact in most habitats humans have colonised within the last hundred thousand years. People forget that fire, spears, clothing, constructed shelters, etc are technology.
Turning to cold blooded probably doesn’t, but evolution most certainly occurs in a generation. It may mean all but a few who manage to survive die but those are the ancestors of the new species
No, mutation or recombination does happen in one generation. Then it has to spread and that needs quite a lot of generations. Mice can have a successful gene spread out in 20-30 years in a local population, humans need a thousand years for the same.
A mutation happens in one individual in one generation. Evolution happens when that mutation propagates through the population by reproduction. That itself takes many generations. Not to mention the fact that the mutation needs to be both advantageous and be recognized as such.
Evolutionary bottle neck events don’t work in such a polite and calm fashion, and there have been many of them.
What happens is 90% of the population (or often more like 99.999%!) that don’t already happen to be carrying an advantageous mutation perish. Sometimes the whole species goes extinct if there is no such mutation already there.
The remainder, if there are any, then don’t have to worry about as much competition, and rapidly reproduce to fill the now mostly empty niche.
It might also just as well disappear again. It's random after all, and when that happens we call it genetic drift. However, it's rare for a gene to be truly neutral.
> Evolution happens when that mutation propagates through the population by reproduction.
Evolution happens when the distribution of genes in one generation differs from the distribution of genes in the previous generation. It happens every generation without fail.
They have the same problems as mammals with high temperatures, but at higher temperatures, because their normal internal temperatures are higher than those of mammals.
