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“”Physics is like sex: sure, it may give some practical results, but that's not why we do it.
Sex can refer to a number of things:
- The number 6 in Latin.
- Biological sex: What kind of sex organs, characteristics, hormones, etc a critter has. If it dangles, it's probably male. If it doesn't, it's probably female (with the noted exception of the spotted hyena[wp]-biologists are still trying to figure out how that happened).
- The action of identifying the biological sex of a (usually newborn) organism (sexing chickens but not having sex with chickens)
- Sexual intercourse: Interpersonal activities involving previously mentioned reproductive organs. Check out our separate article on this subject to learn more!
- Sexual reproduction: When two different critters of approximately the same species each contribute roughly half of their genetic information in the form of gametes, which are then combined to be the genetic information of their offspring, in an embryo or seed of some sort. Closely related species, such as horses and donkeys, are capable of interbreeding, although the offspring are generally sterile. Asexual reproduction is basically cloning. Sexual reproduction, although a simple biological concept, is swaddled in fear and loathing by many odd subsets of the human race.
“”We do not even in the least know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements... The whole subject is as yet hidden in darkness.
|—Charles Darwin, On the Origin of Species, 1862|
The evolution of sexual reproduction has been a mystery to scientists ever since Darwin mentioned the mysteries and problems of it in The Origin of Species. However, since that time, advances in genetics have shone light on how, and perhaps why, the evolution of reproduction occurred. Firstly, a shuffled genetic deck is harder for viruses to latch on to; viruses typically look for stretches of DNA with a specific sequence, and if that sequence happens to cross a recombination boundary in a sexually-reproducing species the virus will be out of luck. Secondly, organisms engaging in sexual reproduction can evolve at a faster rate, being able to create more variations based on sexual recombination of genes. This has been indicated with micro-organisms, where those capable of sexual reproduction adapted more effectively and at a faster rate than asexual organisms. Thirdly, asexual reproduction is at a disadvantage, because any beneficial mutation can only be passed on through direct descendants. With sexual reproduction, the beneficial mutations have a greater ability to spread and the potential to combine with other, complementary mutations.
The very first sexual reproduction is considered to have occurred around 2 billion years ago, sparking an increase in bio-diversity. It is thought that in the first form, sexual reproduction was "optional", a way of reproducing when the organism was experiencing harsh conditions. This is seen today in many species of yeast. Due to the advantages of sexual reproduction described above, sexual reproduction eventually took over asexual reproduction in many species, resulting in the mandatory - and extremely entertaining - activity that we know today.
 Asexual reproduction
|“|| -Can someone tell me who first suggested the idea of reproduction without sex?
-Um, your wife?
—David Lightman (Matthew Broderick), in WarGames
The opposite of sexual reproduction is asexual reproduction, which is reproduction without sexual intercourse.
For many monocellular and even small multicellular organisms, it effectively amounts to self-cloning. The creature grows, copies its DNA into two, and splits into two organisms. Each has the same (discounting copy errors etc.) DNA and is thus effectively the same organism.
Parthenogenesis is the production of offspring by the female of the species without fertilization of the ovum. Some insects and, rarely, reptiles or amphibians have been known to use this method of reproduction.
 Sex vs gender
Usually, a creature's biological sex is congruent with their gender (e.g., none, male, female, intersex, or hermaphroditic).
However, unlike biological sex, gender refers to an individual's self-conception and self-presentation. A person born with male sex organs may feel more comfortable being a woman (or vice versa), and presenting herself as such to society. This presentation, however, is often forcibly suppressed in some countries (socially and/or legally). Many transgender people also take physical steps (such as Hormone Replacement Therapy, and for some, genital reconstructive surgery) to align their physical body/sex with their gender. For example, a transsexual woman would identity as female, socially present as female, and in most cases, take HRT in the forms of estradiol & testosterone blockers. It is worth noting that one's sex cannot be fully changed.
- ↑ https://www.goodreads.com/quotes/117534-physics-is-like-sex-sure-it-may-give-some-practical
- ↑ Zimmer, Carl (5 June 2009). "On the Origin of Sexual Reproduction". Science 324 (5932): 1254-1256.
- ↑ https://en.wikipedia.org/wiki/Sex_change#Sex_change_as_medical_procedure