Watching herd animals on the African plains, it was very easy to see that if they stuck together the Lions would starve. It’s also easy to understand how they could become overpopulated and starve themselves out like that so allowing the Lions to be successful assures their existence. My question is did these animals probably start out more aggressive and lose the aggressiveness later.?
Evolution doesn’t work like that - operating on a whole species all at once. Antelope that run when the lion gets close would survive better than those that didn’t, so the ones that run pass on their genes. The ones that stay and fight are more likely to die, so they don’t pass on their genes. So genes for running stuck around and genes for fighting didn’t.
It’s easy to imagine that animals might act for the greater good of their species, but in fact they do not. There is a strong consensus in evolutionary biology that there is no mechanism by which “group selection” can operate. If an animal were inclined toward any behavior that involved placing greater priority on the well being of the larger group over itself and its kin, that animal would have fewer offspring than another animal that behaved more selfishly. It might appear that a group in which some altruistic pro-group trait were prevalent would be more likely to survive as a group than some other group without the trait. But modeling shows that any potential for natural selection to operate at this group level is always rapidly overwhelmed by natural selection among the individuals within any group, where selfishness prevails.
This “selfishness” does not exclude kin selection (sacrificing yourself in favor or relatives who carry your genes) or cooperation for mutual benefit.
Prey animals like buffalo under pressure from lions do try to stick together as much as possible for mutual defense and to protect their young, and you are right that so long as the group holds together their defense is highly effective. When you see the group break up under predator pressure, they are not “allowing” the lions to succeed. It is simply the fact that they cannot always stay perfectly organized, the lions are always looking for any weakness. If the defensive line starts to fail the urge to simply flee for self-preservation may take hold - in chaos it’s every man for himself in the hope that the lions take someone else.
The venerable E.O.Wilson tried to revive group selection in 2010, but there is a strong consensus that he was wrong. The mathematics doesn’t work.
ISTM that it’s more complicated than that.
There are many videos on YouTube showing lone buffaloes having been downed by lions with the rest of the herd gone, but the herd later returning to drive away the lions and save their comrade. That’s an example of a seemingly altruistic action for a fellow group member without mutual benefit or kin selection.
I suppose the counter-argument would have to be that the instinct which drives the actions of the herd in this situation is favored by selection because that same instinct also comes into play in kin selection or mutual benefit situations. But it makes the picture a lot fuzzier.
How does one draw a line between “kin selection” and “group selection”? The members of any one herd are likely to be much more closely related than members of separate herds, especially if mating isn’t uniformly distributed.
I think you’re combining two things here; the idea of natural selection at work in herding type behaviors, and the idea of equilibrium with respect to herd size, food availability, and predation.
Meaning that there’s probably some sort of behaviors that herd animals have evolved to have that ensure individual survival (and therefore ability to reproduce) by being part of a herd. But those behaviors aren’t group behaviors- they’re something more along the lines of emergent behaviors like fish schooling, or bees swarming- the individual herd animals aren’t acting with any sort of thought toward the herd as a whole, they’re just doing what they’re programmed to do individually, and the overall herd behavior is the aggregate of all those individual behaviors.
The other idea is the equilibrium one. Meaning that a herd will have some size where it’s in equilibrium, based on the availability of food and presence of predators. If you were to put a herd in an area with unlimited food and no predators, that herd size would likely be very large, if not infinte. Think North American Bison, prior to the hunting. But if you constrain food and add predators, that equilibrium size is going to be smaller- I would imagine (IANA biologist) that food availability is the big constraining factor, not predation.
True, a buffalo herd could easily whup up on a bunch of lions, but that is not to their advantage. The lions prevent over population and remove genetic weaklings, providing a group advantage. Herding species use 2 strategies: prey tolerant and prey avoidant. Prey tolerant species expend much less resource on defense than prey avoidant species. Running or attacking are costly. It would be very expensive to gather the herd in order to stampede a few lions.
Evolution moderates populations, not individuals. Botias have spines and frogs have poisonous skin that will kill any predator that swallows them. It’s a trade of one fish or frog for one predator. The advantage is to the prey population, not the swallowed individual. Evolution functions through the gene pool not individual success.
I think this is incorrect - poison frogs evolved as such because it maximized individual reproductive success (they got spat out, and predators started avoiding them). And now predators have evolved aversion to these frogs, because that characteristic improved individual chances at reproductive success.
The same applied to armies before modern weapons. If the defensive line breaks it’s the beginning of the end. Animals have neither communication nor commanders. A ‘leader’ may guide the herd/flock to good pasture, but they don’t stand at the back marshalling the troops.
At some point, you don’t need to run faster than the lions, just faster than your fellows.
Worth noting that perfect equilibrium isn’t necessarily a thing. Some animals have a boom/bust cycle, the classic example being the roughly ten-year cycle of the snowshoe hare and, tracking them in sync, the lynx. Expand until resource constraints cause a population collapse, freeing up resources which causes another expansion. It is an equilibrium of sorts, but not the classic version some people envision of a population cruising along at more or less the environmental carrying capacity.
There are many ways that this may not be pure altruism.
First of all, the “rescuing” buffalo may be related to the downed victim, i.e. this is kin selection. But even if they are not, there is now much less danger for them in going after the lions. Lions always risk life-threatening injury in taking down a healthy adult buffalo, so they will only do it to eat, and they can only eat one buffalo at a time. If the “rescuing” buffalo fail to drive off the lions, they are unlikely to be pursued and killed themselves. The lions will just return to their original easier victim who is already down.
So the risk-reward of attempting a rescue of a downed herd-mate is good, and it can mean that other buffalo may reciprocate in the future. Short-term altruism is certainly possible with non-kin in cooperative arrangements where favors will be returned. And for the future benefit of all the buffalo in the herd including the would-be “rescuers” and their kin, it is always good to send a message to the lions that this herd is not a pushover and there will be no easy meal without serious risk of injury. So this is not ultimately altruistic, just part of a cooperative defense strategy for mutual benefit.
Group selection does not just mean favoring members of your own group over another group. Even where members of a group are not closely related, cooperative traits can certainly arise through “normal” individual selection. In other words, short-term altruism can benefit the individual if favors are returned in the future. This requires social animals with persistent grouping, and sufficient intelligence to monitor other members of the group to ensure that favors are returned consistently. This kind of surveillance in large complex social groups may be one of the major driving forces behind the evolution of human intelligence. Humans are incredibly sensitive to cheating and freeloading within a social group of non-kin, and we place great importance on our own reputation as cooperators. But this is all just “normal” natural selection for cooperative but not ultimately altruistic traits. An individual who is cooperative has superior individual fitness than one who is not.
Group selection specifically means a process where a trait evolves that is truly altruistic with respect to other (unrelated) members of the group. Within the group, an individual with the altruistic trait would have fewer offspring than an individual without the altruistic trait. So it is a process in which a trait evolves that lowers the fitness of an individual relative to other individuals within the group, but increases the fitness of the group as a whole relative to other groups. This proposal has been comprehensively investigated and debunked on theoretical grounds, since there is no population genetic model that works in anything but extremely contrived circumstances. Differential survival among groups is overwhelmed by natural selection operating at the individual level within each group. Traits that lower the fitness of an individual relative to other individuals within the group do not persist, even if they might make your group more likely to survive as a group than other groups.
On average. This is getting into the murky realm of sociobiology and “just so” stories, but there is an argument that we will always have a certain small percentage of sociopaths in society because sociopathy is a successful trait as long as most members of a society are not sociopaths. A society of nothing but sociopaths will collapse. But a limited number of sociopaths in society allows them to sometimes out compete the non-sociopaths because they cheat the rules.
Or lack of empathy might just be a developmental defect that is not strongly selected against because as long as most people aren’t sociopaths, the sociopaths can get by just fine.
Okay, but these complexities are not relevant to drawing the clear conceptual distinction between individual selection and group selection. All of the game theory etc. involved in analyzing potential equilibria of cooperation vs sociopathy is operating at the level of individual selection (if, as you note, the latter trait is adaptative at all).
For modern humans, we should also emphasize the obvious fact that much of what we do is not directly attributable to any innate trait. The fact that an instinct for true altruism cannot evolve by direct natural selection certainly does not mean it cannot exist. We can simply decide to act altruistically because evolution gave us intelligence and we reason that it is the morally right thing to do. Our instinctive altruism may have evolved by natural selection only as short-term altruism in a cooperative strategy with the expectation of reciprocation, but I think we harness this instinct and often choose to act altruistically even when there is no possibility of reciprocation.