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Human Intelligence, Child Rearing and r/K Selection Theory

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In a paper titled Extraordinary intelligence and the care of infantsPiantadosi and Kidd (2016) add to the other hypotheses of higher cognition in humans (Cold Winter Theory and farming) by positing higher cognition evolved to better take care of offspring.

Their theory is that big brained parents have big brained children, with the big brained children needing to be born earlier as their head has to be small enough to pass through the birth canal. A lot of animals can stand up immediately after birth, when humans can’t even hold their head up (I will return to this point later). Human babies are born less mature than other primates, which means they are more vulnerable, thus higher cognition evolved to better care for children. All of the variables coalesce into the need for more intelligent parents, which lead to humans growing more intelligent as a result of this.

They found that weaning time, which acts as a measure of the prematurity of infants, was a much better sign of a primate’s intelligence than any other variable they looked at, including brain size.  Piantadosi said “One of the motivating puzzles of our research was thinking about those theories and trying to see why they predict specifically that primates or mammals should become so intelligent, instead of other species that faced similar pressures.”

The researchers also state that this may explain how humans developed good social reasoning and the “theory of mind” which is the ability to anticipate the needs of others as well as recognizing that other’s needs may not be the same as their own. Kidd also says how the theory of mind is especially helpful since human babies won’t talk for a couple of years. Since women took care of the children, they had to evolve a higher verbal IQ to better care for them. Along with being better able to care for children, men had to evolve high intelligence to care for both the children and women as well as hunt for food and defend his family and other co-ethnics.

Piantadosi and Kidd’s (2016) data shows that the helplessness of a primate’s newborns predict their intelligence, as well as accounting for human uniqueness in intelligence and why this level of cognition took so long to evolve. They also show how dinosaurs, who evolved in the same conditions and had a longer time to do so, did not evolve the same level of super intelligence as primates did. They also matured in eggs, showing that there is no link between intelligence and infant immarurity and birth. Humans also mature slower and need longer parental care. Due to these pressures, a bigger brain evolved. Babies are born earlier and mature slower than other animals, leading to higher intelligence. This also shows how human intelligence is so different from our closest primate ancestors.

This theory compliments the cold winters theory as well as Cochran and Harpending’s argument that higher intelligence evolved due to the advent of farming. Adequate nutrition lead to the development of higher intelligence and bigger brains as well. It also compliments other theories, including that we evolved higher intelligence due to social reasoning and reproductive pressures (sexual selection).

This theory also shows more evidence for Rushton’s Differential-K Theory. As the researchers noted, babies were born less mature than other primates babies. We can also apply r/K selection theory to this as well. Black babies are born one week earlier than white babies who are born one week earlier than Asian babies. Despite black babies being born one week earlier than white babies, black babies can support their heads at 24 hours earlier than white babies. For Asians it’s unknown, as Rushton notes in Race, Evolution, and Behavior (pg. 148). Asian children are slower to develop than white children who are slower to develop than black children, with Asian children having the biggest brains of the three races. This theory of Piantadosi and Kidd (2016) perfectly compliments Rushton’s r/K selection theory. Asians are born one week earlier than whites who are born one week earlier than blacks, which correlates with the average intelligence scores of the three races.

The cold winters theory also shows another reason for bigger brains, as those who evolved in colder climates evolved bigger brains, and therefore higher intellect. The more intelligent parents who could provide more for their offspring prevailed over those less intelligent who could not survive. This lead to more mutations developing in those with high IQ alleles making higher intelligence more prevalent in those populations who evolved further away from the equator, as well as having an adequate population for more births to occur leading to more genetic mutations which leads to higher intelligence. Since those with higher intelligence can survive more efficiently than those with lower intellect, they were able to spread their genes more by having more offspring than those with low IQ alleles (the opposite of what is happening today).

As noted previously from Rushton’s data, those with higher intelligence are born earlier and mature slower than those with lower intelligence. Black children being able to, for instance, lift their head at 24 hours sooner than white children, along with all of Rushton’s data that shows that blacks mature the fastest on all variables. Black children have to mature faster due to a higher mortality rate, which is correlated with low IQ. This is also why black girls have an earlier menarche than white girls. Since black children are born with smaller heads, they, according to Piantadosi and Kidd’s data, have lower intelligence as a result. Black children average smaller brains than white children who averahe smaller brains (and heads) than Asian children. This shows with how Asians are born one week earlier than whites who are born one week earlier than blacks.

This study shows how r/K selection theory is not dead, nor is it not a theory to take seriously, as other researchers have stated since Rushton applied it to race, since it is shown to have good predicitive power. Piantadosi and Kidd’s data corrobarates Rushton’s findings on earlier births between the races, vindicating Rushton and his r/K selection theory. Piantadosi and Kidd show that a) helpless children need intelligent parents, b) intelligent parents must have large brains and c) large brains necessitate having helpless children. This would show, in accordance with r/K selection theory that a) helpless Eurasian children need more intelligent parents, b) Eurasian parents must have large brains and c) large brains nescisstate having helpless Eurasian children.

Piantadosi and Kidd’s theory compliments other theories of human intelligence, which strengthens the cold winters theory of intelligence more, as those with higher intellect have bigger brains, and are therefore born earlier than those with lower intellect and smaller brains. As time goes on, more and more researchers will, unknowingly to them, corroborate more and more of Rushton’s r/K Life History variables. As noted by E.O. Wilson (co-founder of r/K selection theory) in defense of Rushton in the early 90s:

“I think Phil is an honest and capable researcher. The basic reasoning by Rushton is solid evolutionary reasoning; that is, it is logically sound. If he had seen some apparent geographic variation for a non-human species – a species of sparrow or sparrow hawk, for example – no one would have batted an eye. … when it comes to [human] racial differences, especially in the inflamed situation in this country, special safeguards and conventions need to be developed.

As we understand human development more, Rushton’s r/K Life History Theory will be corrobarted. This three-way pattern Rushton noticed, “Rushton’s Rule of Three“, has been corroborated yet again by other researchers. As time goes on, the true nature of humanity, as well as human races, will be revealed unbeknownst to them.

I wonder if Piantadosi and Kidd realize that they have just corroborated one of Rushton’s theories?



    • RaceRealist says:

      Not familiar with it. My knowledge on r/K Life History Theory comes from Rushton. I also read E.O. Wilson on the matter, as he’s the co-founder of the theory. It makes evolutionary sense as well as r/K selection being the best explanation for human differences. I’ll pick that book up when I’m done with my backlog.

      There is a neural basis to political belief. Like all things in life, there is a significant heriatble component. As I noted in my reply to JayMan when he brought up Democrats and Republicans, political beliefs are heritable traits, further proving the existence for genetic similarity theory.

      I love how this theory from Piantadosi and Kidd can be applied to humans. Think they realized this? I love how it corroborates one of Rushton’s theories. It goes hand-in-hand with exactly what he said: more mature babies (Negro babies) are born earlier than the less mature white and Asian babies. Piantadosi and Kidd also confirm that Negro children are born earlier due to their parents having smaller brains, and therefore being less intelligence.


  1. reezy says:

    “Black babies are born one week earlier than white babies who are born one week earlier than Asian babies.

    Asians are born one week earlier than whites who are born one week earlier than blacks, which correlates with the average intelligence scores of the three races.”

    I’m confused, so is the prenatal time black < white < asian, or the other way around?


    • RaceRealist says:

      Whoops. I didn’t catch that.

      It’s blacks who are born one week earlier than whites who are born one week earlier than Asians. Here’s a quote from Rushton’s Race, Evolution, and Behavior:

      Race differences show up early in life. Black babies are born a week earlier than White babies, yet they are more mature as measured by bone development. By age five or six, Black children excel in the dash, the long jump, and the high jump, all of which require a short burst of power. By the teenage years, Blacks have faster reflexes, as in the famous knee-jerk response.

      As you can see, blacks are born one week earlier because they are more mature. White and Asian babes are born less mature.

      Gestation time is blacks earlier, whites intermediate, Asians later. Piantadosi and Kidd’s data shows helplessness, as well as earlier births (which is the reason for the helplessness) facilitated the evolution of bigger brains.

      It’s critical to note that having more children is due to high mortality rate and diseases. So taking environment into account with this, they’re born earlier and slightly more mature, they can have a better chance to pass on genes.

      Since black babies are born more mature, they, later in life, have children earlier in comparison to Eurasians. The average age of first birth was 20 for the Gaza strip, Liberia, Bangladesh, Kenya, Mali, Tanzania, Uganda and various other middle African countries and 28 for Japan, Canada and most European countries. These differences, as noted in the paper, arise due to differences in life history strategy due to the differing environments.


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