Does the theory of evolution fail to explain people sacrificing their lives for their enemies?

Question

Monika i Marcin Gajdowie, "Rozwój. Jak współpracować z łaską", the very beginning of the book:

Przede wszystkim jednak, niektórzy z nas są gotowi oddać życie z miłości do nieprzyjaciół, a to zaprzecza instynktowi przetrwania. Ten absurdalny krok nie daje się wytłumaczyć teorią Darwina.

My translation:

And above all, some of us are ready to forfeit their lives from their love to their enemies. This contradicts the survival instinct; such an absurd act cannot be explained with Darwin's theory.

To give some context: As is evident from later sentences from this book, what I quoted above is one of the few arguments the authors present while trying to support their claim that men "also belong to the supernatural order" (they write from a Christian POV).

This is not, however, what I'd like to focus on in this question.

Instead, my focus is: Does the theory of evolution indeed fail to explain the cases when someone sacrifices their life for their enemies?

Answer 1

And above all, some of us are ready to forfeit their lives from their love to their enemies. This contradicts the survival instinct; such an absurd act cannot be explained with Darwin's theory.

There are two problems with this statement, which make your question whether evolution might actually explain such behaviour, essentially meaningless:

1) The statement assumes that certain actions (which are just assumed/proposed to occur) of individuals go against a 'survival instinct' and therefore contradict the theory of Darwin.

There are a lot of problems with that assumption:

• the 'theory of Darwin' is quite far away from our modern theory of evolution
• Evolution acts on a species, not on individuals. Therefore even if some individuals show a behaviour that is not favourable, evolution still works as normal (and that behaviour may or may not be selected again within a couple of generations).
• Acting against a 'survival instinct' can in principle be beneficial to the survival of the species, even if detrimental to an individual (think of parents sacrificing themselves for their offspring).

2) An 'enemy' is an utterly human concept and has no meaning in the context of evolution or biology.

From a scientific standpoint something like "forfeit their lives from their love to their enemies" makes absolutely no sense.
An individual can sacrifice themselves in certain situations, this may just end their life and therefore be an evolutionary disadvantage. However, - in other situations - it might also help their offspring or other individuals of the species in survival and therefore be an evolutionary advantage. There is no way determine a priori whether such an action will always be beneficial or always negative - both options are possible depending on individual context.

Answer 2

If you're asking if evolutionary explanations of suicide have been proposed... they have e.g.:

The altruistic suicide hypothesis posits that the presence of low reproductive potential and burdensomeness toward kin can increase the inclusive fitness payoff of self-removal. [...]

Altruistic self-destructive behavior has been found in a wide variety of organisms, ranging from unicellular organisms and parasites to social insects, and is debated in mammals. Self-destructive defensive behavior has evolved independently in a number of social insect species in response to natural enemies. Self-sacrificing behavior has mainly been found in the context of nest protection. Defensive self-sacrifice persists in social insects because of its positive impact on the fitness of the colony’s reproductive individuals. As with other forms of altruistic traits, the genes involved will pass on to subsequent generations.

One interesting paper proposed (using simulation) that

Altruism-benefiting fellow group members at a cost to oneself-and parochialism-hostility toward individuals not of one's own ethnic, racial, or other group-are common human behaviors. The intersection of the two-which we term "parochial altruism"-is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one's payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

And I'm not sure people sacrifice themselves for their enemies often enough for that to be worthy of constructing an (evolutionary) explanation for. It might be like asking what's the evolutionary explanation for the moon being made of cheese. Even assuming that this phenotype (sacrificing for their enemies) does occur with some low but non-zero probability (that onus is on you prove it's higher), that doesn't invalidate the theory of evolution for a couple of reasons:

• Selection doesn't act instantly to produce a perfectly fit population, instead fitness increases over time more like a power law, at least in microbes where it's easily quantified. Various loci may be under different levels of selection pressure, depending on the environment. Even assuming the mutation that causes the phenotype is uniformly detrimental to fitness (which might actually not be the case, depending on variations in the environment), weak selection can cause it to linger for a long time; see Huntington's disease as an example of weak selection. (And more recently it's disputed whether the mutations that cause Huntington's provide no fitness advantage whatsoever; the technical term for a tradeoff being "antagonist pleiotropy".)
• Current estimates put the percentage of human genome that evolved due to chance alone to around 5%. Random occurrences of "weird" phenotypes can thus happen with some fairly low probability.