Perhaps, but that statement doesn’t really mean anything in this context. Each “group” will have its own suite of traits which will be advantageous for the environment in which it lives, that other groups in the same environment may lack.
But those traits are prevalent in a population because successful individuals outbred their conspecifics, thus propagating their traits throughout the population. It is the individuals (and their phenotypes) that have been selected for or against, not the population.
Predators single out an individual (we are assuming here that the predator only wants to eat one unit at this feeding time). In a population of 100 here are your odds of survival based on your behavior:
You join the the forming flock: 99/100
You don’t join the forming flock and everyone else does: 0
Those who survive get to pass on their genes. What behavior will the next generation most likely exhibit?
Evolution is primarily driven by competition for resources among individuals. It is therefore not correct to say that “evolution is more about the species”. It’s not really “about” anything. It is a result, not a goal.
This is what seems counterintuitive to me. If predators invariably focus on individuals, then I guess that answers my question. But why would they do that?
Again, I see why they would do that for animals that can fight back, but I don’t see it for defenseless animals.
Since I was apparently wrong about flamingoes being defenseless, let me concentrate on my other example, sardines. If I were a shark, I would MUCH rather swim into the middle of a densely packed school of sardines with my mouth open, than chase individual sardines around.
And it seems like it would take more energy to chase an individual sardine than I’d get by eating it, whereas I could get a full meal almost effortlessly by swimming into the middle of a dense school with my mouth open.
Note that I’m not talking about schools of a few dozen fish that can easily disperse. I may not be recalling the right fish — it might have been herring or something — but one of the nature shows had a segment on small fish that clustered into ENORMOUS schools — must have been hundreds of thousands of them, so densely packed that I don’t see how those in the middle could possibly get out of the way of a speeding predator.
From a population perspective, there are far more individuals in those schools than can be eaten. Even when birds, dolphins, sharks and what have you are all feeding on a sardine school at once, there will be more survivors than there are those who get eaten. Thus, the population survives.
From an individual perspective, it doesn’t matter if he gets eaten, so long as I don’t get eaten. By hanging around several other individuals, the odds improve of me not getting eaten. Obviously, it’s not a guarantee for any given individual.
I don’t think it’s that easy. It seems like it should be, but it isn’t. Going totally at random into a school of prey that can actively dart away from your open jaws yields poor results. (It’s not like filter feeders that swim through plankton, which pretty much just float around passively.)
That’s what I was thinking. And the fewer the individuals eaten, the more genes survive for the species.
And despite all that’s been written here, it still seems to me that, at least for defenseless animals, more would get eaten if they are in the convenient jumbo pack. Somebody said it wouldn’t matter if there is a single predator, and I guess that’s true, but the sardine shoals I was talking about attract great swarms of sharks and dolphins.
Unfortunately, that’s the kind of muddled thinking that comes from a solely gene-centric view of evolution. The genes have no say in the natter - each individual wants to pass on their genes to the exclusion of others. Fred the Sardine does not share 100% of his genes with Robert the Sardine, and it’s those diffrences that each are striving to pass on. Thus, as far as Fred is concerned, it’s great for him if Robert gets eaten; Fred’s genes have a higher chance of being passed on, and Fred doesn’t have to compete with Robert for food and mates anymore. Win-win for Fred!
All that matters, as far as differentiation via natural selection is concerned, is the genetic differences between individuals in the group. If every individual has 100% the same genes, then no variation will ever occur within the species.
However, they don’t - every individual has some mutations in their genes. What determines whether that mutation survives and spreads into the broader gene pool is whether it provides an advantage that is reproductively selected for (or is perhaps coupled with one that does).
I outlined up-thread why “schooling” or “herding” could be selected for in a “every man for himself” population.
One could hypothesize a mutation that caused a sardine to swim outside of the school, but you’d have to show how that mutation gives a reproductive advantage with respect to all the other sardines. Showing that the overall death rate for the group of sardines would be lower is not sufficient.
Yes, I see that. What I’m not seeing is why it’s not a good strategy for Fred to swim the other way when a giant school is forming. The predators are attracted to the school.
It just seems like flocking into the school is like running to where the bombs are landing, instead of away from them.
But I can also see that if you can’t easily find a mate when everybody is split up, that would account for the schooling instinct.
When those giant schools form prior to being fed upon, it’s usually a result of herding by predators (typically, dolphins). As such, and because really, sardines aren’t very bright despite any anthropomorphism I may have engaged in, they don’t really think to leave the school. And if they did, there are predators on all sides who will absolutely scoop them up. Stragglers are typically viewed as free meals, since, far more often than not, that’s exactly what they become.
Perhaps the predator is attracted to the school, perhaps to Fred. For the “swim the other way” mutation to be advantageous, the odds of Fred surviving repeated attacks has to be better than the odds of him surviving in the school. I’m not convinced that they are.
The only muddled thinking comes from not adopting the gene-centric view. If the other individual really did share 100% of his genes – if he was an identical twin or a clone – then it’s irrelevant to his (inclusive) fitness which one of them is eaten. If he shares 50% (full sibling) then the other guy’s life is worth half of his own life. Hamilton’s rule gives the right answer.
I don’t quite know how to respond to this. Based on your user name and the knowledge you have put forth here you seem to be very interested in biology. Still, you are phrasing things in a way that is odd.
Often when I ask students to explain what evolution is they describe natural selection. Sure, that is an important aspect, but if you take natural selection out of the picture evolution will still happen. In no way are the two terms synonymous.
Modern synthesis is about population genetics. We examine the way change is propagated throughout a living system. Currently the smallest quantum of evolution is the gene.
I understand that we are splitting hairs here. But to say evolution is natural selection because it is the primary force is incorrect. Gasoline gives energy to a car, but it isn’t a car.
Two guys are out in the woods and meet a bear. One of the guys turns and runs, the other guy says “dude, you can’t outrun a bear.” The other guy says “I don’t have to, I just have to outrun you.”
Well, you will note that I said “primarily”; few would argue that natural selection isn’t the primary creative force for evolution. I did not say evolution is natural selection!
Further, you may note that I said a “solely” gene-centric view muddles the picture. Selection is hierarchical, acting on more levels than simply the genotype (I am a Mayr-ian / Gouldian, in that I am of the opinion that individuals are the primary, though again, not sole, locus of selection).
Further yet, while I agree that population genetics is a major factor in the modern synthesis, I would argue that it is incorrect to say the modern synthesis is about population genetics. There are many components to the modern synthesis, each of which contribute to our understanding of how evolution works.
I too like this level of selection. Being that there are so many gene interactions there are instances where a gene is selected for even if it contributes nothing beneficial to the phenotype.
Anyhow, hopefully I wasn’t too snarky to a fellow bio nerd. Great user name, btw.
