It's not just mammals and I wouldn't frame it as them being disposable when propagating the species. There's a bigger payout at the right tail of the distribut

It's not just mammals and I wouldn't frame it as them being disposable when propagating the species. There's a bigger payout at the right tail of the distribution for male genes. Male genes can sometimes have 1000 offspring. Female genes generally can't. Male genes are generally more likely to have 0 offspring. So male genes have less to lose and more to gain by taking risks, behavioral and biological risks. See also male variance hypothesis. This varies by species and the pattern is likely stronger in more polygynous species and weaker in more monogamous species. See also sexual dimorphism. Human males take more behavioral risks on average and have higher mortality rates throughout life (not only from behavior). I warn you though, this is a controversial subject because of some of its possible implications. Also I should disclose that I'm not an expert, just a layperson interested in this and some related topics.