2010 October 09 Saturday
How Will Humans Evolve?

Alex Tabarrok and Tyler Cowen have been arguing with each other about how humans evolve. Tyler sees better looking people who are less creative and less driven.

Let us assume that scientific progress continues. My view is that parents don't so much like "difference," unless it is very directly in their favor. Using technology, parents will select for children who are taller, smarter in the way that parents value, better looking, and perhaps also more loyal to their families. The people in the wealthy parts of the world will look more like models and movie stars, but they will be quite recognizable. These children may also be less creative and some of them will be less driven. It's a bit like the real estate market, where everyone wants their house to be special, but not too special, for purposes of resale or in this case mating and career prospects.

Evolutionary biologist Michael Lynch argues that medical advances are making possible a higher rate of collection of harmful mutations in humans. Makes sense. Lots more pregnancies, babies, and adolescents with genetically caused health problems are saved by medical advances and that trend will continue. However, I expect that trend to stop and reverse once genetic testing for embryo selection with IVF becomes widely used to start pregnancies.

My take: Technology will enable humans to make reproductive choices (e.g. thru in vitro fertilization combined with genetic testing for embryo selection) that will reduce some forms of variation in the short run. However, in the long run I expect humans to make decisions that cause divergences that might eventually lead to the generation of multiple new species.

Starting some time in the next 10 years genetic testing will enable embryo selection that will start off the trend toward healthier, sexier, and smarter offspring. That trend will accelerate in the 2020s and 2030s. Therefore in the 2040s and beyond we (at least those of us who live long enough to get rejuvenation therapies that make us young again) will witness a trend toward higher attractiveness. People will become more perfect-looking and more able. Parents will generally want children capable of achieving more success. This will tend to select for intelligence, looks, height, stamina, and motivation. The choices made to get these desired traits will select against genetic diversity in the humans species.

What I'm not sure about: Will a subset of parents go for kids that are more relaxed with personalities that are happy without achieving much success? If so, we could witness a split to two groups in the population where one is hard-charging and wealthy and the other is poorer, lazier, and more content and happy. Granted these types exist today, but more on a continuum. We might witness the development of gaps between the groups with less of middle-of-the road types of personalities.

Genetic variations that reduce desired attributes will get selected against. Notably, all genetic mutations that are only harmful (and we each probably have hundreds of such mutations) will get selected against. Therefore the genetic load in humans will decline.

But in the longer run a number of other factors come into play. One of the weirder ones: People could start tinkering with genes that control just what we find attractive. As people make different decisions about what instinctual desires for mates to put into their offspring different subsets of the human race could diverge into groups that find other groups much less attractive.

What I wonder about: What sorts of personality types will each personality type choose for their offspring once personality type becomes selectable when a pregnancy is started. Will all personality types choose offspring with the same personality type? Or will couples with a pair of personality types have a more dominant member choose the personality of themself for the offspring so that less dominant personalities get selected against? Or will couples make choices for female personalities different than for male personalities so that average male personalities and average female personalities become more different? There are a lot of possibilities and it is not clear to me what choices will be made.

One possibility: People in different cultures will could different choices about offspring personalities and other qualities. So humans in different regions could diverge from each other to become more unalike. However, a drive toward higher intelligence offspring might have the opposite effect since very smart people might all reach more similar conclusions about what attributes are most ideal for offspring. It is not clear to me how this will go.

By Randall Parker    2010 October 09 10:47 PM   Entry Permalink | Comments (43)
2010 June 08 Tuesday
Neurotic Women In Poor Countries Make More Babies

Neuroticism and extraversion are being selected for in countries with the highest birth rates.

The study, which was published yesterday (7 June 2010) in the Proceedings of the National Academy of Sciences, found that women with higher levels of neuroticism and more extravert men, are likely to give birth to a larger number of children in societies with traditionally high birth rates.

I'd really like to know which personality traits are being selected for in Western industrial societies. Natural selection has not stopped. But in industrial societies selective pressures change. Since more educated people have fewer kids intelligence is being selected against. But what other cognitive traits are selected for or against?

Women with higher neuroticism were also less able to feed their children well.

The study also found evidence of a link between maternal personality traits and offspring´s physical condition, as women with higher neuroticism levels were more likely to have children with a decreased body mass index (BMI), reflecting malnutrition.

The existence of a wide range of personality traits might represent competing reproductive strategies where some women have more kids who suffer child mortality rates while other women have fewer kids and suffer lower child mortality rates. Relative reproductive success of the two strategies might vary over time as food availability waxes and wanes.

See the mention here of previous work in Western populations. Anyone know what the research has found on fertility and personality traits in the West?

Personality traits are increasingly being studied to understand individual-level determinants of fertility patterns, and how differences in personality can be maintained by natural selection. Previous work has been carried out in modern Western populations, but the current research was conducted in a more traditional population, enabling the team to test how personality affects fertility rates in a `natural environment´ characterized by high birth rates.

Humans are still evolving. That does not mean they necessarily are becoming more advanced. Rather, they are experiencing selective pressures and different genetic variants are getting selected for and against.

Human evolution accelerated in the last 10,000 years. The ability to do in vitro fertilization (IVF) embryo selection using genetic tests with detailed knowledge of the meaning of different genetic variants will soon cause an even greater acceleration of human evolution. Offspring will be chosen before embryo implantation to maximize desired traits and minimize undesired traits.

By Randall Parker    2010 June 08 10:25 PM   Entry Permalink | Comments (11)
2010 May 13 Thursday
Tibetans Genetically Adapted To High Altitude

Tibetans carry several genetic variants that adapt them better to high altitude living.

SALT LAKE CITY—Researchers have long wondered why the people of the Tibetan Highlands can live at elevations that cause some humans to become life-threateningly ill – and a new study answers that mystery, in part, by showing that through thousands of years of natural selection, those hardy inhabitants of south-central Asia evolved 10 unique oxygen-processing genes that help them live in higher climes.

In a study published May 13 in Science Express, researchers from the University of Utah School of Medicine and Qinghai University Medical School in the People's Republic of China report that thousands of years ago, Tibetan highlanders began to genetically adapt to prevent polycythemia (a process in which the body produces too many red blood cells in response to oxygen deprivation), as well as other health abnormalities such as swelling of the lungs and brain (edema) and hypertension of the lung vessels leading to eventual respiratory failure. Even at elevations of 14,000 feet above sea level or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells and do not develop lung or brain complications. The Utah and Chinese researchers found evidence that this might be related to at least 10 genes, two of which are specific genes strongly associated with hemoglobin, a molecule that transports oxygen in the blood.

Tibetans have had more time to evolve for better fitness at hgh altitude than other groups that live at high altitude. For example, the Amerinds in high altitude areas of Peru have genetic adaptations to altitude but their adaptations aren't as sophisticated (sorry, no cite, read this a few years back). Evolutionary pressures haven't acted on them long enough to bring forth the best genetic variants for high altitude living.

Han Chinese are not genetically adapted well to high altitude. Tibetan women give birth to bigger babies than Han Chinese women at the same high altitudes. The Han Chinese women have more adverse pregnancy outcomes at high altitudes.

Various human populations around the world evolved to better adapt to local conditions. Immune systems, digestive tracts, skin color, height, and other physical attributes and functions evolved pretty rapidly once humans left Africa. This evolution was probably sped up by mating with Neandertals.

I am curious to learn which personality and other cognitive traits were seleced for to adapt humans to local environments. For example, did being a fisherman work better for certain personality types while other personality types worked well for crop farmers or herdsmen?

By Randall Parker    2010 May 13 05:52 PM   Entry Permalink | Comments (5)
2009 June 10 Wednesday
Virginity Incidence In Adults

UCSF urologist Michael Eisenberg finds that among virgins aged 25 to 45 church attendance and college education increased the odds of virginity.

His team's survey found that 13.9 per cent of men and 8.9 per cent of women said they have never had sex.

Men and women who attended church at least once a week were respectively 5 and 3.9 times more likely to be virgins than those who attended church less often. Virgins of both sexes were slightly less likely to have swigged a beer in the last year, compared to non-virgins. And women with college degrees were 5.4 times more likely to be virgins than women who never got their Bachelor's.

Note the higher incidence of virginity among church-attending men than among church-attending women. I had a girlfriend who attended church (unlike myself) who complained to me that too many of the guys at church were basically pussies. Not masculine enough for her. Islam seems more designed to appeal to men. Perhaps mosques pull in more masculine Muslims?

I see this as a sign that church attendance and intelligence are both being selected against. What other signs of evolutionary natural selection in humans do you see happening?

Update: Currently high IQ is getting selected against in the US. Though as that link suggests, the selective pressure might be declining somewhat. Similarly, in Australia intelligence looks like it is getting selected against while Catholicism is getting selected for (which is not surprising). Also, Catholic and Protestant women are more fertile in the United States. But can anyone point to a good data source on male fertility and church attendance or religious belief?

Update II: Audacious Epigone chomping on some numbers from the General Social Survey (GSS) and the GSS reveals that higher fertility of religious couples makes up for any virginity of single Christians. The faithful are out-breeding the unbelievers.

By Randall Parker    2009 June 10 11:48 PM   Entry Permalink | Comments (29)
2008 October 10 Friday
Humans Evolved Egalitarianism In Pleistocene Era

The Pleistocene era that ended 10000 years ago saw the development of human societies less hierarchical than other ape societies. How did this happen? A mathematical model of human social structures suggests that the development of egalitarian human societies came about in a small number of generations.

Although anthropologists and evolutionary biologists are still debating this question, a new study, published in the open-access journal PLoS ONE, supports the view that the first egalitarian societies may have appeared tens of thousands of years before the French Revolution, Marx, and Lenin. These societies emerged rapidly through intense power struggle and their origin had dramatic implications for humanity. In many mammals living in groups, including hyenas, meerkats, and dolphins, group members form coalitions and alliances that allow them to increase their dominance status and their access to mates and other resources. Alliances are especially common in great apes, some of whom have very intense social life, where they are constantly engaged in a political maneuvering as vividly described in Frans de Waal's "Chimpanzee politics".

In spite of this, the great apes' societies are very hierarchical with each animal occupying a particular place in the existing dominance hierarchy. A major function of coalitions in apes is to maintain or change the dominance ranking. When an alpha male is well established, he usually can intimidate any hostile coalition or the entire community.

Note that humans still place great importance in status and power. A substantial portion of human behavior is aimed at achieving and demonstrating higher status. The human shift toward a more egalitarian model has been only partial. We still have plenty of genetic influences on our brains that make us desire higher status and power. Possibly human populations differ in their frequencies of alleles for egalitarian preferences versus hierarchical tendencies based on different selective pressures in different parts of the world.

In sharp contrast, most known hunter-gatherer societies are egalitarian. Their weak leaders merely assist a consensus-seeking process when the group needs to make decisions, but otherwise all main political actors behave as equal. Some anthropologists argue that in egalitarian societies the pyramid of power is turned upside down with potential subordinates being able to express dominance over potential alpha-individuals by creating large, group-wide political alliance.

What were the reasons for such a drastic change in the group's social organization during the origin of our own "uniquely unique" species? Some evolutionary biologists theorize that at some point in the Pleistocene, humans reached a level of ecological dominance that dramatically transformed the natural selection landscape. Instead of traditional "hostile forces of nature", the competitive interactions among members of the same group became the most dominant evolutionary factor. According to this still controversial view, known as the "social brain" or "Machiavellian intelligence" hypothesis, more intelligent individuals were able to take advantage of other members of their group, achieve higher social status, and leave more offspring who inherited their parent's genes for larger brain size and intelligence. As a result of this runaway process, the average brain size and intelligence were increasing across the whole human lineage.

I like this "Machiavellian intelligence" hypothesis. But we also evolved higher intelligence in order to better manipulate tools and our physical environment. Our spatial reasoning was probably not selected for in order to better engage in Machiavellian intrigue.

As people became smarter they became more able to form alliances against dominant alpha males. So intelligence increased the bargaining power of betas? Did the rise in human intelligence then cause a selection for personality traits characteristic of betas?

Also increasing were the abilities to keep track of within-group social interactions, to remember friends and their allies and enemies, and to attract and use allies. At some point, physically weaker members of the group started forming successful and stable large coalitions against strong individuals who otherwise would achieve alpha-status and usurp the majority of the crucial resources. Eventually, an egalitarian society was established. Although some of its components are well supported by data, this scenario remains highly controversial. One reason is its complexity which makes it difficult to interpret the data and to intuit the consequences of interactions between multiple evolutionary, ecological, behavioral, and social factors acting simultaneously. It is also tricky to evaluate relevant time-scales and figure out possible evolutionary dynamics.

A paper published in PLoS ONE today makes steps towards answering these challenges. The paper is co-authored by Sergey Gavrilets, a theoretical evolutionary biologist, and two computer scientists, Edgar Duenez-Guzman and Michael Vose, all from the University of Tennessee, Knoxville.

They developed a computer model to reach their conclusions. Keep in mind that two different computer models might produce the same result (greater sharing of resources in alliances) with different assumptions and mechanisms. We can't tell whether ideas in the minds of Pleistocene humans or genes that coded for alliance-oriented behavior were the bigger driving forces. One can easily imagine these two influences feeding on each other though.

Ideas in the head of one "cave man" (or should I say "savannah man"?) could have caused that guy to look at all the other people in his group and seek out those whose personalities were most amenable to alliance formation. Any genetic alleles that favored alliances could have been there for other reasons but the thoughts in one mind could have caused one guy to reach out to those with compatible genetic alleles and get them all to behave in ways (e.g. fighting as a group and splitting spoils evenly) that promoted the spread of those alleles.

To develop egalitarian societies larger scale conflicts are needed. This puts a much more positive spin on war, doesn't it? Having external enemies to focus on helps keep alliances together.

The model also highlights the importance of the presence of outsiders (or "scapegoats") for stability of small alliances. The researchers suggest that the establishment of a stable group-wide egalitarian alliance should create conditions promoting the origin of conscience, moralistic aggression, altruism, and other cultural norms favoring group interests over those of individuals. Increasing within-group cohesion should also promote the group efficiency in between-group conflicts and intensify cultural group selection.

A better organized group is going to wipe out less organized groups. Once group-level organization gets a foothold any genetic variants that helped favor it would get selected for and spread. Higher intelligence might have catalyzed the spread of alleles for higher intelligence and alleles for greater egalitarian behavior.

Is communism not possible because the spread of egalitarian alleles hasn't gone far enough? Too many of the old hierarchical alleles are still around? I suspect another explanation: The egalitarian alleles were selected for to enable groups to compete with other groups. Humans competed for resources and for the vast bulk of human history resource limitations made hunger widespread and the competition for resources fierce. Egalitarianism and competitive urges are key elements of human nature and egalitarianism's development came about to help people compete more effectively.

See also Cochran And Harpending See Human Evolution Acceleration and Cochran And Hawks Detect Human Evolution Acceleration.

By Randall Parker    2008 October 10 12:15 PM   Entry Permalink | Comments (17)
2008 August 31 Sunday
David Friedman On Evolution And Human Nature

David Friedman says that while Leftists generally accept that evolution occurred they reject all implications evolution has for human nature.

People who say they are against teaching the theory of evolution are very likely to be Christian fundamentalists. But people who are against taking seriously the implications of evolution, strongly enough to want to attack those who disagree, including those who teach those implications, are quite likely to be on the left.

I think he is right on his basic points. The bulk of the (fairly unscientific) attacks on the idea of genetic causes of differences in intellectual performance come from the Left. The argument for the primacy of social environment as the biggest force determining our intelligence comes from the Left. Yet some genetic theorists find evidence that local selective pressures exerted even over several hundred years can cause big changes in cognitive function. Friedman starts out focusing on differences between the sexes in cognitive function.

Consider the most striking case, the question of whether there are differences between men and women with regard to the distribution of intellectual abilities or behavioral patterns. That no such differences exist, or if that if they exist they are insignificant, is a matter of faith for many on the left. The faith is so strongly held that when the president of Harvard, himself a prominent academic, merely raised the possibility that one reason why there were fewer women than men in certain fields might be such differences, he was ferociously attacked and eventually driven to resign.

Yet the claim that such differences must be insignificant is one that nobody who took the implications of evolution seriously could maintain. We are, after all, the product of selection for reproductive success. Males and females play quite different roles in reproduction. It would be a striking coincidence if the distribution of abilities and behavioral patterns that was optimal for one sex turned out to also be optimal for the other, rather like two entirely different math problems just happening to have the same answer.

Human male and female brains differ in fundamental ways. For example, women have a higher ratio of white matter to gray matter than men. The scientific literature on male-female differences in cognition is now enormous. Yet a president of Harvard (Larry Summers) can still get forced from office in part because he took that scientific literature seriously.

Speaking as someone who thinks the evidence for the theory of evolution is overwhelming I am very disappointed at how evolution has been walled off from most discussions of human nature in the political sphere. Among most secularists (who like to fancy themselves as more scientific than the Christians) I see widespread embrace of a sort of modern Cartesian dualism where instead of placing the mind in a supernatural realm the genes that code for the mind are viewed as immune to evolutionary selective pressures. We are supposed to believe that humans have evolved so far that they've escaped the genes that code for their minds and that at birth the human mind is a Blank Slate (tabula rasa) almost totally molded by its environment.

I see the Left's Blank Slate as an even worse model for understand human nature than the fundamentalist Christian Original Sin view of human nature. The Original Sin model maps closer to what evolution produced: selfish desires that got selected for in order to cause behaviors that boost reproductive fitness. In the Original Sin model the idea that evil can be defeated in this world is laughable because the devil is whispering in everyone's ear and the battle between good and evil is constant. The temptations of sin are the desires and instincts placed in us by millions of years of natural selection. So the idea of Original Sin hits a lot closer to the truth than the view that we can perfect humans with smarter social policies. New Soviet Man is the antithesis of what a Darwinist ought to think is possible to achieve in human societies.

A June 2007 article from Plos Genetics, Localizing Recent Adaptive Evolution in the Human Genome, provides examples of localized evolution of cognitive function.

Several genes with functional roles in the development and function of the nervous system show very strong evidence (CLR p < 10−5) for a recent selective sweep. For example, SV2B, a gene encoding a synaptic vesicle protein with highest expression during brain development [36], exhibits strong evidence for a selective sweep in the African-American sample. Likewise, the protein encoded by DAB1 plays a developmental role in the layering of neurons in the cerebral cortex and cerebellum [37], and exhibits strong evidence for a selective sweep in the Asian sample. Other nervous system genes with strong evidence for a selective sweep include two candidate genes for Alzheimer disease (APPBP2 and APBA2) that bind the amyloid-beta precursor protein, two genes (SKP1A and PCDH15) with a role in sensory development, and several others with various roles in nervous system development and function (PHACTR1, ALG10, PREP, GPM6A, and DGKI).

A March 2007 article from Plos Biology, A Map of Recent Positive Selection in the Human Genome, finds plenty of signs up local cognitive evolution.

Recent articles have proposed that genes involved in brain development and function may have been important targets of selection in recent human evolution [8,9]. While we do not find evidence for selection in the two genes reported in those studies (MCPH1 and ASPM), we do find signals in two other microcephaly genes, namely, CDK5RAP2 in Yoruba, and CENPJ in Europeans and East Asians [46]. Though there is not an overall enrichment for neurological genes in our gene ontology analysis, several other important brain genes also have signals of selection, including the primary inhibitory neurotransmitter GABRA4, an Alzheimer's susceptibility gene PSEN1, and SYT1 in Yoruba; the serotonin transporter SLC6A4 in Europeans and East Asians; and the dystrophin binding gene SNTG1 in all populations.

This all is unsurprising and I expect much more evidence to be uncovered of cognitive adaptations to local environments. For example, fishermen had different cognitive demands placed on them than farmers. With a boat one is in constant danger of death and one needs to be much more careful. The ideal personality for a crew member of a fishing boat is probably different than the ideal personality for a sheep herder and the ideal personality for a sheep herder is probably different than that for a tiller of soil. So an area with lots of coastlines and little farmable land probably have different average personality types than areas with lots of tillable soil.

While some will rush to dismiss these speculations evidence has already begun to emerge that genetic variations that affect cognitive function make people more adapted in some environments and less adapted in other environments. For example, a genetic variation that contributes to hyperactivity boosts success of nomadic tribesmen but makes them less successful when they move into urban environments. A lot of people with Attention Deficit Disorder (ADD) and Attention Deficit Hyperactivity Disorder (ADHD) probably have what we consider a disability in industrial society because their ancestors did better by having the genes that cause these cognitive states. Today ADHD causes people to be more violent and criminal.

While politically correct dogma would have us believe that humans are extremely similar excepting for appearances the latest genetic research shows that human groups are evolutionarily diverging from each other and in many ways. But these insights from research are entirely missing from political discussions.

As my regular readers know, I think we are on the verge of an enormous explosion of discoveries about human genetics and the roles genes play in causing differences in cognitive function, athletic performance, health, and other aspects of human function. People who anchor their political beliefs in either supernatural religious or secular religious belief systems are going to find the foundations of their beliefs blown away by this coming torrent of discoveries.

By Randall Parker    2008 August 31 11:15 PM   Entry Permalink | Comments (56)
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