do you know from when in evolution history, there are two sexes?

Question

what superiority it has for animals that has two sex ?

and why?

and why?

How it started?

Answer 1

Many organisms have various combinations of asexual and sexual reproduction. But you are not asking about the origins of sexual reproduction ... but about sexual reproduction with two dedicated sexes (which came much later).

Sexual reproduction in reptiles (and other cold-blooded animals, and most flowering plants) does not involve genetically determined sexes. Individuals are either hermaphrodites (have both sex organs), or gender is determined by temperature during gestation.

The development of warm-bloodedness (regulating the body temperature) allowed sex of the offspring to be determined by hormones, rather than temperature, during gestation.

The type of sexual reproduction we are familiar with ... dedicated sexes determined by the presence of an X or a Y chromosome ... developed in mammals about 300 million years ago (based on genetic evidence). In other words, the hormone environment that determines sex was not keyed to the mother, but by the genetics of the offspring. Offspring that had a Y chromosome produced the hormones that caused development into males, those with only X chromosomes developed into females.

The advantages of dedicated sexes (i.e. the reason that it stuck around, instead of all individuals being hermaphrodites), are (a) that this makes embryology much more efficient ... the embyo doesn't have to dedicate energy developing both types of sex organs; and (b) it takes a lot more energy to be a female ... so there are advantages to the species if some, or many, individuals are males.

(Aside: The common question "why do men have nipples?" is related to this, and in fact is evidence of a remnant of hermaphrodite ancestors. The reason males have nipples is that these develop in all embryos at a stage *before* the hormones determine the sex.)

BTW, the word "superiority" does not apply in evolution ... the word "advantage" is more correct (because it points out that advantage is relative ... it depends on the environment). Asexual reproduction and hermaphrodite sexual reproduction have advantages too for certain types of organisms ... which is why the overwhelming majority of life on the planet (one-celled organisms) still use asexual reproduction. But for warm-blooded animals in particular, who are already spending a huge amount of energy in regulating body temperature, the development of genetically determined sexes is not only possible, but has many advantages as far as conserving energy during development.

Answer 2

That arose very early in life (even very simple organisms may have sexes, and many bacteria show 'quasi-sexual' behavior (they exchange genetic material through a process called conjugation) even though they have no obvious division into different sexes.
The purpose of sex is to increase adaptability of the population; by mixing the genomes, all sorts of combinations can be produced, which gives you a wide range of varieties of abilities to deal with the variety of conditions you face in life. Some will do better than others in a particular set of conditions, and tend to pass on their combinations better. The problem, of course, is that if you _have_ to mix your genes every time you make a kid, then even if you luck onto the perfect set of genes, your kid won't have them. Some plants do it best - they make seeds by sex to get a diversity of abilities, and the plants that come from those seeds that survive in a particular area produce identical copies of themselves using root shoots or other clonal growth.

Answer 3

January 21st, 200 million BC

Answer 4

i'm guessing when they start to form multicellular organisms