A Question About Evolution?

Question

How did 'sex' and 'gender' evolve? How infinitely improbable is it that two creatures randomly envolved into other creatures that are made for each other?

Answer 1

One thing you miss ... and none of the answers have mentioned ... is that sexual reproduction and dedicated genders are two separate questions ... separate developments. A species can have sexual reproduction, but NOT have specialized genders.

This means that there doesn't have to be a sudden jump from asexual reproduction to full sexual reproduction with different genders.

For example, the majority of flowering plants use sexual reproduction but do NOT have dedicated genders ... all individuals have both male and female parts. While this is very common in the plant kingdom and in parts of the animal kingdom, it is not common in our branch, the vertebrates. The reason is that having both male and female organs is wasted resources in embryology, and this is a disadvantage in more complex animal embryos.

So the bottom line is that there are *many* different reproductive methods used in all species ... many combined in the same species.
- Some bacteria reproduce mostly asexually, but with occasional mixing of genetic material between individuals.
- Some organisms can reproduce both sexually or asexually depending on the availability of mates.
- Some species go through different sexual or asexual phases in their lifespans.
- Some species use only sexual reproduction, but all individuals are both males and females (no specialized genders).
- Some species use sexual reproduction, where individuals go through different male or female phases.
- Some species use sexual reproduction, where gender is determined by environment (e.g., bees, where gender is determined by what the larva is fed).
- And some species use sexual reproduction, where gender is determined during the embryo stage, based on genetics (the system used by vertebrates like us).

Not only do the above indicate intermediate stages in the evolution of reproduction, but because there can be different combinations of reproduction systems even in the *same species*, it indicates how transitions can occur *between* those stages ... a species can go from using one system primarily, and slowly evolve into a species that uses a different system. For example one where gender determined in early life, to one where gender is determined during embryology ... only one set of sex organs develop.

(Incidentally, the old "why do men have nipples?" question is evidence of this. Nipples in males are remants of early stages of embryological development before gender is expressed in the genes.)

So it is a mistake to think of males and females as two separate "creatures" (as you put it) that somehow found or were "made for each other" ... males and females are part of the same "creature" ... the only difference between males and females of our species is a single chromosome.

And finally, one other point that I can't let slide:EVOLUTION IS NOT RANDOM. Mutation is random, but natural selection is the very NON-RANDOM effect of environment and the act of survival.

Answer 2

Evolution is all about reproduction so it does not at all seem improbable that creatures evolved into genders. Simpler organism are often both genders and can reproduce asexually (without sex).
A species evolves towards traits that make the species stronger. If an animal cant survive long enough to mate and reproduce then it will not be able to pass on it's genes to the next generation.
I would think that it made survival easier when some members of a species were free to hunt and gather while others gave birth to young. I would imagine that pregnancy would make an animal easy prey.

Answer 3

Well. I can't truly say how they evolved, but there are some advantages to having 'sex' and 'gender'. By having sex, the genes of the said species is mixed and forms a new version of itself that is far more protected from being wiped out because not all of the species would succumb to the same disease. And gender goes along with that theme. It allows the mixing of the genes by each creature providing half of the information needed. It sounds improbable, but hey, there are lots of more bizarre evolution survival tricks. Like creatures getting out of the water in the first place.

Answer 4

I don't think there is an answer to how that began. As Bekki said, sexual reproduction results in a lot more variation which is a chief driver of evolution. This would have been a huge advantage that would have caused the eventual extinction of non-sexually reproducing species. This is another key question that has yet to be answered, as is the question of how the very first life could have come to be.

Answer 5

Let me see if I can answer your question from a more realistic point of view. One, there is no advantage to sexual reproduction. Take for instance E. coli a bacteria that reproduces asexually. It has thirty percent diversity of it genes, compare the human species a sexual creature it has about .1 percent biological diversity. Two, humans while they reproduce sexually every so often (like10 years), actually reproduce asexually much more often. The somatic cells in our bodies reproduce every few hours with a few exceptions.
If you want the probabilities they are easy to calculate using a Markov matrix. Let say an asexual species mutates in to two sexes with a probability of .00001
M F Sum
M .99999 .00001 1.0
F .00001 .99999 1.0
Fitness 1.0 1.0
Multiple this matrix times itself about 100000 times for each generation and it will result in what is known as a stationary probability for the genders or .5 for Males and .5 for Females. This the usual sex ratio at mating time for sexual creatures.
The fact that the fitness is 1 for both is the only way to end up with this sexual ratio. Hence there is no advantage to being a male or female. There really is no Darwinian explanation for this. Try Kimura Neutral Theory or Jukes and Kings Non-Darwinian Evolution Theory.

Answer 6

Your first question is good. Looking through the many examples of life on this planet, we have examples of reproduction that are asexual and many variations of sexual, that include hermaphroditic animals, dikaryotic fungi, dioecious plants. You should look these up and see the evolution (or change) in sex and gender. You can calculate the probabilities later (which is small, but obviously happened).

Answer 7

'sex' is a characterisitc feature of complex organisms. The progeny out of this process are more fit to survive and eventually live longer. Organisms like Microbes mostly don't mate with each other coz they normally don't have to lead longer lives! So, simply they split themselves into two! (Binary fission) Evolution to other organisms is not by chance! but by sheer necessity! Best example is ourselves. Imagine, our brains get more sharpened and therefore we have lesser necessity to use our limbs where they eventually reduce in size and utility!

Answer 8

Sex arose as simple exchanges of genetic material between very simple creatures. It is evolutionarily successful because sexual reproduction leads to greater variety than vegetative reproduction. Consequently, populations that have sex are more resistant to plagues and evolutionary challenges of all sorts. Once you have sex going on, of course the genders will evolve so that to a naive observer, it might appear that they were "made" for one another.

Answer 9

I'll check in the Origin of Species. My guess is that organisms became too complex to keep reproducing by cellular division. As for your second question, your conclusion of "that they are made for each other" doesn't make sense. When was the last time that you saw spiders going to the movies?

Answer 10

sex is a biological factor determined your dna, if you have xx you are a female if you have xy you are a male.

gender however is a cultural and sociological name given to a culturally based set of behaviors and is usually confused with sex or terms are used interchangibly.

but technically speaking your sex and your gender really are too different things entirely. unfortunately the common terms used to define gender are feminine and masculine, and that tends to link them to sex.