(November 5, 2014 at 3:13 am)Aractus Wrote: Yes, but biology isn't concerned with abnormalities. As I just showed you, people with XY chromosomes who have androgen-insensitivity syndrome are biologically considered to be male. Other areas of science define sex/gender differently to biology, but the OP asked the question about biology and the answer is that every human is distinctly male or female from the biological perspective irregardless of development abnormalities.

What about those with Turner's Syndrome? They have only one X chromosome.

EDIT: Nevermind. Just read the part in another of your post that answers this question.

(November 13, 2014 at 1:05 am)Reader Wrote: The next question: (we now understand why we didn't evolve into 7 or 7000 "sexes") ... is at what point did we go from being asexual to being sexual (2 sexes) in order to reproduce?

A long time before humans, and in fact many species continue to reproduce asexually, and some species that do reproduce sexually can in fact self-reproduce asexually (e.g. some sharks). If we were to take sharks as an example, one could well argue that there wasn't fixed a "point" when a species switched to sexual reproduction, but rather that at some point it became available as a means of reproduction, and that overtime evolution geared towards sexual reproduction.

In the case of humans and other mammals, we rely solely on sexual reproduction. So the the role of asexual reproduction was diminished, ultimately to the point that asexual reproduction no longer provided a meaningful function to the species and it was dropped. We are unable to initiate parthenogenesis naturally and reproduce asexually, although at some point in the past one of our biological ancestors would have been able to (for reference that process means the female's ova self-conceives producing an embryo genetically identical to the mother). So in the same way that we can no longer use our appendix for anything, we also can no longer use our original means of asexual reproduction.

The other thing to consider is that male and female sexes were not originally assigned by genetics, and as I previously mentioned it is still the case for many species that environmental factors and not genetics determine whether an organism develops into a male or a female. This is obvious simply by the fact as I previously mentioned that the ZW sex chromosomes determine sex in exactly the opposite way of the XY sex chromosomes.

So in short the answer is that the "point" you're enquiring about refers to a time perhaps millions of years ago when sexual reproduction began to be trialled alongside asexual reproduction, and overtime evolution generally geared towards sexual reproduction producing the modern species we have today that are now unable to asexually reproduce.

Hope that helps.

http://aebrain.blogspot.de/p/transsexual...ntity.html

We know that MZ, but we're discussing biological sex not psychological gender identity. The two sciences are very different and have very different opinions on the definition of gender. Feel free to start a separate thread to discuss psychology.

(November 4, 2014 at 8:01 pm)Chas Wrote: Two sexes, some number of genders.

The two human biological sexes clearly had an evolutionary root, as very similar strategies of sexual reproduction are found in the animal kingdom. I'm not sure if there is any evidence for any organisms with more than two sexes involved in reproduction.

As for gender and transgenderism, additional genders (beyond a masculine/feminine binary) can also relate to one's upbringing or nurture as well as culture, and involves issues of personal identity and selfhood, particularly relating to gender and biological sex.

I have personally known several people of both genders who had a rough time with socially prescribed gender roles, some of whom considered themselves transgendered.

Its the way it is, and that's all, there's female and male, one has a doddle and one doesn't, its that simple.

Hi welcome

Looks like you got plenty of good answers.

(November 5, 2014 at 10:20 pm)Aractus Wrote: Whiles those are valid issues, they are not relevant to human biology. Humans cannot biologically be intersex, although they can have (as mentioned before) serious abnormalities.

Such as fucked up sexual chromosomes http://en.wikipedia.org/wiki/Klinefelter_syndrome is one example of what I'm talking about, but it depends on what you mean by "biologically intersex".

Quote:It is possible for some birds and some other animals to be intersex, the condition produces an adult that is biologically male on one side and biologically female on the other (split vertically left-right). such intersex creatures can be fertile - meaning they can be both the paternal and maternal parent of an offspring. In other creatures sex/gender can be determined environmentally and not genetically, and in some creatures they can change their sex from male to female (or the other way) as an adult in a single sex environment. Again, humans can't do this, and although environmental factors can produce serious abnormalities in development, it can't determine gender. It is biologically impossible for a human to develop both an ovary and a testicle. The human gonads cannot develop separately into the two distinct sexes, as can happen (as mentioned) in birds.

Sounds painful. I see what you're contention is... and I agree.

Quote:Biologically speaking, a person with a single X chromosome is a female. A person with three X chromosomes is a female. A person with XXY chromosomes is a male.

This is not meant as an attack on your community, just on the exact biological definition of sex/gender.

Thank you for clarifying The definitions of both sex and gender are so often disputed and have so many variations that it tends to take hours to come to common ground, explaining that kind of intricacy... I wasn't in the mood, and I apologize for that

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(December 3, 2014 at 2:43 am)psychoslice Wrote: Its the way it is, and that's all, there's female and male, one has a doddle and one doesn't, its that simple.

So if I cut off the one's 'doddle'....?

Making females! Making females! Lalalala!

(November 22, 2014 at 7:38 pm)Aractus Wrote: We know that MZ, but we're discussing biological sex not psychological gender identity. The two sciences are very different and have very different opinions on the definition of gender. Feel free to start a separate thread to discuss psychology.

Opps, sorry about that mate

(November 13, 2014 at 1:05 am)Reader Wrote: Sorry I've not posted in several days. The classes I'm teaching are new, so there's a lot to prepare each week. I've read all of the responses and shared them with my students last week. They appreciated the feedback. If it's alright, I'd like to post questions that the students may come up with or need clarification as we cover different topics. We are just seeking to comprehend.

Sorry I'm late to the party.

What Evolution Is and Is Not
Regarding the first question, I think we need to emphasize that evolution is not about whether or not there is a god. Evolution could involve a yet-undetected deity that oversees the process. Science doesn't deal with this because it only concerns itself with the natural universe, or that which can be studied.

Neither is the case that Creationism is necessarily a reference to the Christian god (one can be a Muslim Creationist, a Hindu Creationist, etc.).

Evolution, in my layman's understanding, boils down to two observations:

1. Life changes over time.
2. Changes that benefit survival or adaptation to a given environment will be more likely to be passed on.

In my home state of Kentucky, horse breeding is a profession we're known for (and for our famous springtime horse race). We breed horses to be faster. This is "artificial selection", where humans interfere with the process, but "natural selection" the driving force of evolution, works the same way only over longer periods of time.

Why Two Genders?
There are biological advantages and disadvantages to both asexual reproduction and sexual reproduction.

Advantages of Asexual Reproduction
1. It's quick and easy. A cell divides into two cells. Done.
2. It only takes one organism.

Advantages of Sexual Reproduction
1. Greater variation in offspring as two sets of genes are mixed and matched.
2. Said variation results in more changes in fewer generations, thus greater adaptability as the environment changes.
3. Some genes can be "recessive", carried by the organism, to be passed on and possibly appear in later generations, and thus retained by the gene pool to allow for greater variation.

Greater variation = quicker adaptation = biologically beneficial
...but, to quote the Sonny and Cher song, "It takes two, baby"

Why Not More Genders?
More genders would increase the variations even more, that is true, but as with all things, there is a diminishing return of benefits and an increased cost at each level. Already, sexual reproduction is more "complicated" than asexual reproduction.

Consider the time and energy we spend finding the right partner. Then think of all we go through managing a relationship with that partner. Now multiply that with a third gender. And again with a fourth. Etc.

The genetic variation gained by such increased complication would likely not be worth the added complication. Two gender reproduction already yields a suitable variation in the mixing and matching of genes.

Quote:The next question: (we now understand why we didn't evolve into 7 or 7000 "sexes") ... is at what point did we go from being asexual to being sexual (2 sexes) in order to reproduce?

Well, we haven't really. Asexual reproduction still takes place in simple life forms on the planet. Single cell organisms, bacteria, maybe fungus.

At least some plant life does have male and female characteristics, playing a role in reproduction. I remember studying in school that the early research on genes was conducted by Gregor Mendel. To get around the moral issues of studying sexual reproduction in animals, he restricted himself to the study of plants. This was where we discovered "dominant" vs. "recessive" genes and how they are passed down through the generations.

Worms, by the way, are hermaphroditic. When two worms run into each other while crawling through the ground, they gain the greatest biological advantage by impregnating each other.

So as we move from single cell organisms to plant and animal life, it seems we find more examples of sexual reproduction and fewer of asexual reproduction. Exactly what are the most complicated of organisms that still have asexual reproduction, a biologist can answer better than me.