The climate seems like a very topical issue, constantly being brought to the forefront of the political arena. Newspapers comment, governments pledge and bloggers quarrel…all in the here and now.
Given all of this, it’s easy to forget that the environment has been constantly changing since our planet first formed. It isn’t just a current issue, everything you see and hear has been shaped by aeons of climate variability.
When I say aeons, I mean aeons: humanity has only existed since around the “r” in “warmer”
Including us, Homo sapiens. We are the children of climate change. And not just in the sense that it was one of the many factors that influenced our evolution. No, a paper published last summer purports that climactic variability was one of the primary driving forces behind the emergence of the lineage which gave rise to you and I.
And not just us either. Back before everyone’s favourite closest relative, Homo neanderthalensis, we lived alongside dozens of related species. Several variates of Australopithecines, Paranthropines and Homo(ines?) lived side by side in ancient Africa. Most of them eventually went extinct, but our ancestors continued on to become the success story. Why? Once again, the answer seems to be climate change.
But let’s not get ahead of ourselves. Before understanding how the climate picked us over our cousins, lets look at how this much maligned process did something creative and prompted the development of many new species?
Yes that’s a silly question, but then people also ask how explosions create order. The world is full of silly questions.
Evolution, ya’see, does this thing called “adaptive radiation” in which, upon entering a new environment, an organism will diversify into a variety of forms. It does this because this new environment will be full of new niches a range of organisms can exploit. Thus, instead of having just one organism trying to be the best at one thing, there is room for many organisms doing many things.
“But,” I hear you say, “look at the graph you just posted. There isn’t any new environments appearing, it’s just constant variation.” Ah, but climate variation can have a similar effect as the creation of a new environment.
If there’s just a warm environment, only warm adapted organisms will flourish. If it’s an environment that fluctuates between hot and cold, suddenly there’s space for cold adapted creatures to start developing. New niches are created by new variability, even if the absolute environment remains pretty much the same.
And if you look at when the climate was the most variable in the past few million years, sure enough you see it’s ~2.5-1.5 mya, when the hominin lineage starts to diversify into a myriad of forms.
The grey bit is when the climate is extra variable
Amongst the variety of new possible specialisations a variable climate creates, it also creates the opportunity to not specialise. If an environment is fluctuating between hot and cold, both cold and hot adapted animals will be favoured. But if an animal is well suited to both the hot and the cold? It’ll kick evolutionary ass!
And – as you should already know – that’s what we (or, more accurately,Homo erectus) did. We decided “jack of all trades, master of none” was actually a fairly good motto and became specialised at being generalists.
But is not the “master of none” part a concern? Although we might have been well suited to a variety of environments in each of those we would be second place to someone who was well adapted. However, in a fluctuating environment even being second best can win you cold.
For example, if you have a generalist and a warm specialist in an environment that fluctuates warm/cold the following would happen. First year is warm, you (the generalist, remember?) have 2 babies, the specialist has 3. The next year is cold so you have another 2, the specialist has none. Third year is warm again, so he has another 3 and you have 2 bringing the total to…6 each?
Not quite. See, your babies also had babies and have been geometrically increasing. He has 3, you have 2. Then you have 2, your babies each have 2 (they’re fast growers) and you have 6 total members of your species. Then the specialist has another 3, making them 6 total whilst your 6 individuals double again to become 12.
Still with me?
So, climate variability made room for new species and allowed us to diversify. One of these organisms was a generalist and so coped well with increasing variability and eventually out-competed all these variants. This species gave rise to Homo sapiens.
Well….
This study isn’t perfect. For starters, it merely identifies a correlation between when diversification/generalisation occurred and when the climate is variable. And, as you all should know, correlation does not mean causation.
The second flaw was pointed out when this work was presented at HOBET: the climate data used covers a wider area than Africa where we evolved. Thus, the specifics of the climate our ancestors lived in might be different which would alter the results somewhat.
However, all the modelling is set up. All the researcher needs to do is input some African data and see if his conclusions still hold true.
I look forward to that.
| Grove, M. (2011). Change and variability in Plio-Pleistocene climates: modelling the hominin response Journal of Archaeological Science, 38 (11), 3038-3047 DOI: 10.1016/j.jas.2011.07.002 |
Asking how an explosion can create order is a silly question?
Please give me just ONE observable example of that.
Because the big bang wasn’t an explosion, at least not in the traditional sense. Trying to draw an analogy between dynamite and the starting conditions of the universe just falls flat on its face.
I did not use the word dynamite, but you DID use the word explosion. So, you are conceding the point that an explosion cannot create order?
Yeah, I just didn’t fancy repeating the word explosion twice in the same sentence so substituted it for dynamite to make it look nicer. Sorry about that.
My point was simply that asking whether an explosion can produce order (in regards to the big bang) is a silly question because it wasn’t an explosion, thus the analogy is flawed.
I’ll say an explosion always results in a net loss of order, but not that it is always totally chaotic. Some order can still be retained/produced, but overall it will be lower than what you started with. Nuclear bombs, for example, produce a mushroom cloud which is rather ordered (but still less so than the original bomb). This isn’t directly relevant to the big bang (I think), I’m just trying to be as accurate on the physics as possible. Which is hard, given I find the whole field rather daunting.
Of course, this all stems from an off hand joke. Do you have any comments on the main thrust of the article itself?
It isn’t the explosion, of course, but we do know that simple rules can allow order to form from chaos. In the case of the BB, the laws of physics and gravity provided the rules that allowed structure to form from the chaos of the BB.
Big conundrum regarding all that though… laws of thermodynamics require entropy to increase in a system. This implies that, somehow, the BB was an extremely low entropy event.
Which explosions are rather considered to be the opposite of, so it’s a problem.
If there’s one thing I’ve learnt about physics, its that “big bang” is an awfully misleading misnomer.
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