Chapter X and Y: Conflict (Genome)

•Linguistics has led to the discovery of evolutionary psychology, which has unsettling implications for free will.

• The X and Y chromosomes are known as the sex chromosomes because they determine the sex of the body.

• There are things about the X and Y chromosomes most people do not know, including that they are in a battle with each other.

• A recent textbook on the material is entitled “Evolution: The Four Billion Year War”.

•The X and Y chromosomes often have genes that are beneficial for one sex but detrimental to the other.

• One example of this is the DAX gene, which is found on the X chromosome. People with two copies of this gene develop into normal females, even though they are genetically male.

• This conflict between genes can be dangerous for the species as a whole. For instance, a gene that kills only sperm carrying Y chromosomes would spread quickly and could eventually exterminate all males from the population.

• Most known instances of sex-chromosome drive are confined to insects, but this is likely because scientists have looked more closely at insects than other animals. Any gene on the Y chromosome is vulnerable to attack by a newly evolved driving X gene.

•The SRY gene is responsible for the masculinization of the brain and body, and is one of the fastest evolving genes.

• Selective sweeps occur when a driving gene on the X chromosome attacks the Y chromosome, resulting in a new SRY gene sequence being shared by all members of a species.

• William Rice’s experiments show that male ejaculate contains proteins that enter female bloodstreams and alter their behavior in ways beneficial to males.

•Sexual antagonism is at work in all sorts of environments and leaves its signature as rapidly evolving genes.

• The traditional view of the peacock’s elaborate tail is that it is a device designed to seduce females and that it is in effect designed by ancestral females’ preferences.

• Rice and Holland come to the disturbing conclusion that the more social and communicative a species is, the more likely it is to suffer from sexually antagonistic genes.

•Evolutionary biologists believe that bigger brains were needed in an arms race between manipulation and resistance to manipulation.

• The phenomena we refer to as intelligence may be a byproduct of intergenomic conflict between genes mediating offense and defense in the context of language’.

• In 1993, Dean Hamer found a gene on the X chromosome that had a powerful influence on sexual orientation.

• Homosexuality is highly heritable.

• If a man was gay, the most likely other member of the previous generation to be gay was not his father but his mother’s brother.

•Trivers argued that, because an X chromosome spends twice as much time in women as it does in men, a sexually antagonistic gene that benefited female fertility could survive even if it had twice as large a deleterious effect on male fertility.

• Suppose, for example, that the gene Hamer had found determined age of puberty in women, or even something like breast size (remember, this is just a thought experiment). Each of those characteristics might affect female fertility.

• Until Hamer’s gene itself is found and decoded, the link between homosexuality and sexual antagonism is no more than a wild guess.

• The birth order effect is so strong that each additional elder brother increases the probability of homosexuality by roughly one-third (this can still mean a low probability: an increase from three to four per cent is an increase of thirty-three per cent).

• An important clue lies in the fact that there is no such birth-order effect for lesbians, who are randomly distributed within their families. In addition, the number of elder sisters is also irrelevant in predicting male homosexuality. There is something specific to occupying a womb that has already held other males which increases the probability of homosexuality.

YARPP List

Related posts:

1. Law 17: Seize the Historical Moment (The Laws of Human Nature)
2. Part 2: Isolate the Victim (The Art of Seduction)
3. Chapter 16: The Capitalist Creed (Sapiens)
4. On Nietzsche’s Thus Spoke Zarathustra Summary (8.4/10)