While it’s not the reason we have 2 sexes, there is an evolutionary reason for 2 partners to make an offspring, which is likely a big contributing factor
While asexual reproduction is easier, the downside is that the child is almost an exact genetic match of the parent. There’s a lot of reasons why this is not ideal (I don’t remember them lol, its complicated), so having 2 organisms mix their genes to create a genetically unique offspring is extremely advantageous. Having 2 sexes is likely easier than doing this with a unisex species, but as another commenter pointed out: evolution doesn’t make sense, it just does what works.
It seems to be the demands of large terrestrial mammals. Land is a harsher environment where more genetic diversity from sexual reproduction is more advantageous. Being larger and having longer lifespans makes asexual reproduction rarely advantageous. One parent needing to gestate the offspring would exacerbate the pressures for sexual dimorphism. Almost no mammals asexually reproduce, in fact it might actually be none, but I’m not sure.
While it’s not the reason we have 2 sexes, there is an evolutionary reason for 2 partners to make an offspring, which is likely a big contributing factor
While asexual reproduction is easier, the downside is that the child is almost an exact genetic match of the parent. There’s a lot of reasons why this is not ideal (I don’t remember them lol, its complicated), so having 2 organisms mix their genes to create a genetically unique offspring is extremely advantageous. Having 2 sexes is likely easier than doing this with a unisex species, but as another commenter pointed out: evolution doesn’t make sense, it just does what works.
It seems to be the demands of large terrestrial mammals. Land is a harsher environment where more genetic diversity from sexual reproduction is more advantageous. Being larger and having longer lifespans makes asexual reproduction rarely advantageous. One parent needing to gestate the offspring would exacerbate the pressures for sexual dimorphism. Almost no mammals asexually reproduce, in fact it might actually be none, but I’m not sure.