130. Human Behavioral Biology: Intersexual Competition & Male/Female Hierarchies

10 lessons from this lecture:

00:04:17 The same optimization building blocks discussed at length on the previous lecture on the collision of game theory and evolution about genetics can also be applied to behavior:

  1. Do whatever is possible to pass as many copies of your own genes into the next generation as possible.
  2. Help your relatives pass their genes into the next generation; this can sometimes be the best way for you to ensure that your genes are passed on into the next generation.
  3. Reciprical altruism: You scratch my back, I’ll scratch yours which allows un-related and dissimilar animals to peacefully coexist.

00:13:11 Babies, regardless of the animal, are always adorably cute and you want to take care of it and protect it. Their eyes dilate as soon as you’re around them and field biologists believed up until about the 1970s that:

  1. Everything about a baby’s characteristics are to demonstrate reduced aggression. 
  2. Humans were the only animals that killed for pleasure

[EDITOR’S NOTE: Recall in the mini-documentary Sex & Love: Interpreting Body Language & Non-Verbal Cues as well as in their book The Definitive Book of Body Language, Allan & Barbara Pease explain that the ‘eye pop’ is effective because closing the eyes dilates the pupils. Dilated pupils are synomomous with attraction and need for protection. Babies’ pupils are typically dilated in an evolutionary attempt to demonstrate to its caregivers that it should be protected and cared for.

In advertising, female and baby model’s eyes are almost always photoshopped so that they are dilated. Doing this naturally draws the potential consumer’s attention to the model, and then to the product being sold. For more advertising tricks, browse through my interviews with advertising professionals.

Conversely, Allan & Barbara Pease explain, the opposite of dilated eyes are ‘beady, snake-like eyes’ which give the impression that you are shady, untrustworthy, and dangerous.]

Field biologists have since proved that infanticide exists in many animals.

00:14:14 The first response to reportings of infanticide was denial – arguing that there must be some sort of abnormal pathological behavior going on.

However upon further investigation behavioral patterns emerge explaining the role of infanticide in the species:

  1. It tends to be the adult males who kill the infants.
  2. It tends to  be adult males who kill the babies of other males – competitive strategies for reducing another male’s reproductive success.
  3. It tends to be more common in competitive species where the average inter-birth interval among females is longer than the average tenure of a high ranking male. Meaning if you’re not the alpha-male, then your best chance at becoming the alpha-male is to kill the alpha-male’s babies and then have your own babies, thus decreasing that male’s potential for reproductive success, and because the female will begin ovulating shortly thereafter.

This behavior is a blatant violation of the idea of behaving for the good of the species.

[EDITOR’S NOTE: For more information on pathological behavior, browse through the lectures and interviews under the How To Shape Human Behavior: criminal profiling category.]

00:18:49 An alpha-male challenger would be less inclined, however, to kill all of the alpha-male’s babies in situations where the alpha-male is the challenger’s brother or relative. In some species, such as in rodents and horses, the presence of a new male causes pregnant females to release certain stress hormones which disrupt uterine maturation which leads to miscarriage.

This has developed through evolution because the female, in an attempt ot pass as many copies of her genes into the next generation, is faced with one of three options, the third of which is the most evolutionarily efficient: 

  1. Continue on having the baby, only for it to be killed by the alpha-male challenger after the baby’s birth, or 
  2. Have a miscarriage and become a potential partner for the new alpha-male, or
  3. Go into pseudo-estrus, in which the pregnant female demonstrates signs that she is ovulating when in fact she isn’t, the male is tricked into believing she isn’t pregnant, and thus the new male doesn’t kill the baby after it’s birth believing the baby is his.

This entire process is obviously male-bias, with the female making the best out of her situation. Following the principle of passing your genes into the next generation, it’s observed that older female mothers will be more protective of their children because their ability to turn around and have another child diminishes with age, whereas younger mothers have more time and opportunity to have more children.

00:27:35 It has also been observed in some species of monkeys that when two monkeys are about to fight, the smaller, weaker monkey may grab a child and hold it against it’s chest. But the smaller monkey isn’t just grabbing any enfant monkey, it’s ‘kidnapping’ children likely to be the offspring of the stronger, high-ranking monkey.

00:32:22 In a competitive tournament species where 5% of the male population actually have children, having a male is a big gamble that he will not pass his genes into the next generation. Having a female, who will grow up to have from 1-5 children, is a much greater advantage and ability to pass her genes into the next generation.

It follows that it would be more advantageous for females who are in higher-ranking families to give birth to males, whereas it would be more advantageous for females who are from lower-ranking families to give birth to females.

00:33:40 With the human species, typically the human sex ratio is approximately 1:1. However in certain parts of the world, and during periods of famine and ecological duress, the percentage of females being born should increase because female fetuses require less caloric intake and strain to the mother’s body than male fetuses, which also makes the mother more vulnerable.

00:37:39 Polyandry is the practice of one woman having multiple husbands at the same time. In nature, for example among lions, it may be two brothers sharing the same wife, thus ensuring that the genes are passed from one generation to the next. This is known as adelphic polyandry, or fraternal polyandry.

Adelphic polyandry is even evidenced in humans, for example in traditional, rural Tibetan society where in agriculturally impoverished areas where a family with land inheritance has several sons, dividing the land among the sons would put each son below subsistence level. So rather than dividing up the land, they create a family which is one reproductive unit where one woman is married to all the sons.

01:00:42 The controversial notion of group selection which has creeped back into biology is when one small group of a species becomes somehow isolated from one another, and continue on mating and reproducing independently. Eventually, the smaller isolated group becomes more inbred simply because there is a smaller, less diverse gene pool, thus making family ties among the group more intricate.

Kin selection states then that cooperation among the members of the smaller, more closely-related group will be much higher than cooperation among the larger groups because of the higher  degree of relatedness.

If the smaller, more cooperative group of the species then somehow reenters into the larger group, the more cooperative group will begin outcompeting the rest of the group, which will slowly conform to the smaller group. This is referred to as the Founder effect.

In the financial world, an example of this could be when one small, cooperative group offers each other flexible, low interest loans, which increases the financial success of that small group. Slowly, other non-group members will begin joining the smaller group and benefiting from the advantages of their cooperation and trust model.

It follows then that although A>B, BB>AA. 

Meaning: if “B” is making flexible, low interest loans to just anybody, he will be dominated by “A,” who makes inflexible, high interest loans. However if “BB” are making flexible, low interest loans to members of their own community, they will dominate “AA,” the group who makes inflexible, high interest loans.

01:34:22 There are many arguments against this theory, however the most controversial is perhaps the socio-political implications which lead to questions like:

  • “Are there species of humans which are genetically inferior to others?”
  • “Is rape a human psychopathology or a competitive strategy?”
  • “Is the fact that children are more likely to be killed by step-fathers than by biological fathers a form of infanticide as individual selection?” Noting above that it tends to  be adult males who kill the babies of other males – competitive strategies for reducing another male’s reproductive success.

166. Human Behavioral Biology: Species Evolution On A Molecular Level

09 takeaways from this lecture:

00:03:05 Recall from the previous lecture Intersexual Competition & Male/Female Hierarchies that heritability is the notion that, until proven otherwise, behaviors are genetically influenced.

On a molecular level, proteins are made up of roughly 20 amino acids coded for a different DNA sequence, and there are roughly 60 different ways of coding for amino acids. These roughly 20 amino acids are structurally responsible for holding your cell shapes together, forming messengers, hormones, neuro-transmitters, enzymes… Proteins are what get your cells to do what they are supposed to do.

One of the most interesting things that proteins do is act as enzymes which speed up the process of putting together and pulling apart molecules.

If you know the sequence of DNA, then you’ll know the sequence of RNA, the amino acid sequence, the resulting protein that is made as well as the shape and function of the protein. This tenet has since been disproved.

The central tenet in molecular biology of how life and information flows, as proposed by British molecular biologist Francis Crick was DNA>RNA>Protein; that DNA determines everything. This tenet has also since been disproved:

  • Viruses are foreign DNA which hijack another DNA and force it to do what the virus wants it to, thus changes the RNA and the proteins.
  • There is also a class of enzymes which can attack RNA and turn it back into DNA and then hijack it for it’s own objectives.

00:17:10 Micro-mutations are when one letter in a DNA sequence is accidentally miscopied or changed by radiation or some other chemical compound. Broadly, one of three mutations occurs:

  1. A point mutation is when one letter in the DNA sequence is changed into another letter.
  2. A deletion is when one of the letters in the DNA sequence gets lost.
  3. An insertion is when one of the letters in the DNA sequence gets doubled.

00:27:03 In modern times, 12 years old is the Westernized average time little girls start puberty and begin menstrating. Testicular Feminization Syndrome is a condition where genetically the human is a male complete with testes which make testosterone, but the testes never descended, and so is mistaken for a female.

All of these protein and receptor mututations effect humans evolutionarily in slow, predictable and incremental changes; changes we can identify and predict.

00:40:51 FOXP2 is an example of a genetic protein mutation that happened to humans, and is what gave humans the ability to develop speech and language. Versions of FOXP2 occur all throughout the animal kingdom.


You share 98% of your DNA with chimpanzees, yet on average only 50% of your DNA with your full siblings. To simplify, genes specify traits: kidneys, bones, antlers, etc. So right from the start you share genetic similarities with other species which also have kidneys, bones, pelvises designed to walk upright, etc. Why you have less genetic similarity with your full sibling versus with a chimpanzee comes down to coding not for the different genes, but for the different ‘types’ of genes. This is a different world of variance.

00:52:31 In the 1980s Steven Jay Guld and Niles Eldredge came up with the theory of punctuated equalibrium: that evolution isn’t being driven by small gradual changes, but rather long periods of stasis where nothing changes followed by short periods of rapid change, and then back to stasis.

The logic behind punctuated equalibrium was due mainly because Guld, a Marxist, wasn’t a biologist, but rather a paleontologist who studied fossils and traced the evolutionary lineage of change in a species through time. In the world of paleontology, you don’t have clear logical steps showing the evolution of a species as viewed from their fossils, but rather gaps in time which can neither be explained nor tracked. And as more and more data are discovered about the species, you see great similarities over time, and then gaps in the evolution where things had changed drastically over a short period.


This theory flies in the face of the idea that genetics are passed down through competition and that the strongest survive. Not surprisingly, those scientists supporting survival of the fittest weren’t happy with Guld and his punctuated equalibrium, and they attacked his theory in several sound ways:

  1. Paleontology and a evolutionary biology come from completely different universes and measure time through different orders of magnitude.
  2. Paleongology is only concerned with the fossils and morphology of organisms, not the smaller genetic modifications such as brain activity and development, behavior, and the number of chambers in the animal’s heart, etc.

01:07:10 Nobel Prize winning biologist David Baltimore found that one gene can have its protons and exons combine in many different ways. This finding was also ill-received by the scientific community which held that one gene only specifies one single protein with no variation.

A shocking 95% of your DNA is junk DNA, or noncoding DNA. This noncoding DNA acts as the instruction manual for the coding DNA

01:25:14 If then clauses in the molecular genetic world: IF you get a signal that there is low glucose in the cell, THEN you begin to make proteins related to glucose uptake. IF you smell your child, THEN you’ll experience a particular reaction.

01:29:16 Are genetics fixed or malleable based on the environment? Mothering style, such as how often a mother wakes her baby, can cause permanent changes to genes related to stress hormones, dictating how readily some genes will be turned on or off for the rest of your life.

Epigenetics is the study of “variations that are caused by external or environmental factors that switch genes on and off and affect how cellsread genes instead of being caused by changes in the DNA sequence.” The researcher Steve Sumi who studies primate social behavior found that by simply changing the style of mothering that a baby monkey receives, and you change the confirmational access state of +4,000 different genes.

Fertilization is all about genetics; development is all about ways in which the environment shapes behavior.