Thread by @realscientists

Morning! Let's talk evolution: what it is, how it works, in particular why no one should ever say the phrase SURVIVAL OF THE FITTEST ever again, on any occasion, under any circumstance, for the rest of human history.

Evolution needn't be biological. It's a process, and it NECESSARILY happens whenever a system has these three raw ingredients:

THE RAW INGREDIENTS OF EVOLUTION
1) A population of things that produce offspring with similar properties
2) Mutations that occasionally change these properties
3) A selective mechanism that makes the rate of replication depend on those properties

Or for a T-shirt: HERITABILITY, MUTATION, SELECTION.

Any system that has these three properties MUST evolve. Not just life. We can program evolutionary systems into a computer and use them to optimise airplane wings, for example. sciencedirect.com/science/articl…

In biological evolution, a popular idea is that an optimum reproductive strategy is big, strong, smart, powerful, alpha. An idea perhaps perpetuated by the behaviour of some animals and its reflection in the trope of a Gengis Khan type warlord and his harem.

This reproductive strategy exists, but it just can't be the norm, which we can prove logically. If big'n'strong were always the best way, we'd all have maximised it to physiological limits by now. But most animal species are small, and the biggest'n'strongest are extinct.

That's because almost EVERYTHING in biology is a tradeoff. For instance, big is hugely energy costly and starves in winters, requires more work to regulate temperature and pump bloody, accelerates slowly and lacks nimbleness, maturation takes longer, is hard to camouflage, etc.

As cichlid fish show, there are many reproductive strategies to trade off between. Being a good resource gatherer. Being resilient to cold/hot. Forming social ties is a massive one, cooperation is hugely efficient. Being a good offspring carer. Being innovative or creative, etc.

What's more, populations are dynamic. If one strategy becomes popular, it opens niches for alternative strategies. The 'sneaky fucker' phenomenon notes that in male-macho-dominated species (eg cuttlefish), a subgroup of "feminine" males arises to undercut that strategy. It works.

Evolution is just too creative and dynamic to favour simple optimisation for 'macho' traits. A population of machos will favour the evolution of strategies to outcompete it. And just as well. The diversity of human physical and behavioural traits is glorious, don't you think?

No there's a subtle discussion that desperately needs to go here, but I will do it in another post. That is gene-centred evolution. This is the concept that explains (among a million things) why co-operation is often a better strategy than selfishness. But word limits are arse :(

So "survival of the fittest" should be replaced with? Since it's impossible to say what will be most reproductively successful across all possible settings, all we can say is that those genes which get passed on persist. So: "Survival of the genes conferring replication success".

But IMHO, the best replacement for "survival of the fittest" is just the ingredients that necessitate evolution: HEREDITY-MUTATION-SELECTION. Because you can figure everything else out from them alone. And take it from my hero Charles, figuring things out is life's greatest joy.