AnthroHealth
Something
New Under the Sun:
Adapting to Change in the 21st Century
AnthroHealth News
August 2006
Volume 5, Issue 8
Greetings!!
Heat waves are rolling across North America and Europe causing temperatures to spike into the triple digits in many places unaccustomed to such heat. The eastern portion of the United States has experienced widespread flooding. We haven’t yet seen devastating hurricanes the equal of Katrina or Rita, but the season still has weeks to go. Why do we care about the weather? Because it is something we can’t control. It is one of the few things that can slap us in the face to let us know that as much as we might like to think otherwise, we are still a part of nature and still subject to its whims. Ignoring that fact can lead to poor health and even death. Being aware of our interactions with nature can allow us to optimize our health.
Book Club: Several AnthroHealth News readers have commented that they are enjoying the book club discussion of Dawkins’ A Devil’s Chaplain, and a few are reading the book. However, only Dr. Iczkowski has once again provided specific chapter-by-chapter feedback on Part 2, Light Will Be Thrown. As with last month, below each of his review/commentary sections are my own comments on that section.
Part 2, Light Will Be Thrown: 2.1 Light Will Be Thrown
K.I. This section is devoted to “sexual selection,” comprising a major part of The Descent of Man. In most species, males are “marked” and females are unmarked; males advertise their health, good provider status, and desirability and females do the choosing. The male may have bright feathers, colorful wings in the case of butterflies, more colorful fur, big antlers, or even colored genitals (vervet monkeys). In most species, males visually attract females, but in humans, the reverse is true. It is noteworthy that in humans, it is mainly women who decorate their bodies so as to be marked: brighter colored clothing, makeup, jewelry, hair styling, clothes that show their curves, etc. Women’s magazines such as Cosmopolitan and Glamour are all about how to attract men, but men’s magazines are about looking at women. The problem with this comparison is that we cannot strictly compare the natural attributes of other species with the artificial decorations of humans, but the uniqueness of human sexuality may help explain these differences.
Dawkins goes on to say that the scientific climate in which Darwin wrote is before Mendelian genetics. Most scientists previously to Mendel believed in the blending hypothesis, that genetic traits were not particulate but would blend. Counterintuitive to this theory is the realization that this would give rise to greater uniformity in each generation: all men would be the same height and all women the same height, for instance. Sex itself--the fact that there are no intermediate hermaphrodites but that males and females persist through the generations—also supports the particulate theory of inheritance.
The stable sex ratio in most species tends toward 50-50. However, parental investment can alter it. If for instance, it took twice as many resources to rear a male as a female, then the stable sex ratio would be twice as many females as males. Is the percent of males lower than females for gorillas, in which the male is so much larger than the female?
Continuing with the parental investment theme, the mother typically invests more energy than the father in rearing offspring. This explains why males are more promiscuous and compete with each other, whereas females are more selective. Certainly, in most human families including my own, the dad is the second-fiddle parent...even if he tries hard to be a “modern” dad and participate more in family life than his grandfathers.
Is parental investment also paramount in deciding how many children to have? Modern Western society is a statistical aberration in human history in that mean number of children per woman is 2.2 in the USA, and 1.4 in Russia—below the replacement rate. Yet, during most of human history, large families were the norm. Our “founding fathers” were biological fathers to a much greater extent than today’s men. Alexander Hamilton, for instance had 8 children (and had time to have an affair!). In the third world—Africa, Asia, South and Central America, large families are still the norm. One would think, in countries where resources are most abundant, people could produce more children. Why doesn’t the average American family have 16 children—double Hamilton’s number? I can think of these reasons:
1) Parental investment to raise a child has skyrocketed. It costs a quarter-million dollars to raise a child through college and give them a car and other goodies. And the value of a college diploma has fallen, so postgraduate education is almost a necessity for a nice lifestyle...costing more money.
2) Children used to be an asset, working to support their family (farming or industry), whereas today they are perceived entirely as a liability. Furthermore, they remain a liability for a longer time. Economically it is very hard for young adults to make it alone. Consequently, we have adultolescents—kids living at home well into their 20s or 30s.
3) Percentage of children born who survive to reproduce is much higher thanks to obstetric and medical advances. Contraception is readily available. Lifespan has doubled since the 1700s, so the number of generations alive at a time is higher and there are fewer resources to go around to support children.
The expectation that modern parents have to DO so much for their children, more than their own parents ever did, probably precludes investment in a large family. These factors all support a conscious decision, in Western societies, to have a small family.
Dawkins talks about the human genome (DNA content) being 98 percent the same as chimpanzee DNA. However, based on the number of genes that are exactly the same, the figure would be close to zero. The percentage similarities is a “molecular clock” that allows us to see when species diverged. This is analogous to radioactive dating of fossils. One change that occurred since our split from chimpanzees is neoteny: the resemblance of descendants of a species to younger individuals of the older species. Adult humans resemble young chimpanzees.
Finally, the topic of “race” with regard to sexual selection is covered. The existence of races is stated to be based on different regional, cultural, standards for sexual selection. But, to what extent this selection is aesthetic versus due to disease seems to me to be debatable. Dark skin and its protective function from skin cancer in low latitude is balanced with light skin and its protection from vitamin D deficiency in high latitude. Whether this equilibrium in skin tone resulted from death of individuals with the “wrong” skin color, versus sexual selection for the “right” skin color, is worthy of speculation. Maybe both processes were at work. That is, early Nordic European humans recognized dark skin as undesirable because it was associated with individuals with rickets, so light skin became sought after as aesthetically desirable in its own right.
K.F. While current fashions focus on female decoration, men are always advertising their reproductive status. As with other ape species, human females of reproductive age prefer, on average, males who are older than they are, but not old. Females judge males by comparing (generally, subconsciously) facial bone structure, facial hair, and body mass. Males with strong faces, a beard (current fashions dictate it be shaved off), strong shoulders, and a muscular upper body are viewed as more attractive than males with more delicate bone structure, no beard, and a slim, gracile build. Phenotype indicates sexual maturity and is a proxy for genotype. That is, in the not-too-distant past, males who arrived at sexual maturity in good health showed good adaptability and survivability which are indications of good genes. There is a biological basis for the romantic stereotype of tall, dark, and handsome. “Tall” stature indicates both maturity and that the male was well fed as a child and is, therefore, probably healthy. “Dark” is also associated with maturity since adult males tend to have somewhat darker skin tone than do females; in part, this may be due to their hairier bodies. One who is handsome (or beautiful) tends to have symmetric features and that, in turn, is associated with absence of obvious genetic problems and presence of good health. Consciously or not, human females of reproductive age are looking, on average, for good genes when they select a male as a mate.
The folk belief that traits blend is behind much of the confusion about races. First, there is only one race: human beings. Second, for most traits, there are multiple genetic variants called alleles. You get one set of alleles from each of your parents. For single gene or monogenic traits, figuring out the genotype/phenotype combinations is fairly straight-forward. But for multiple gene or polygenic traits, such as skin color or hair type, the analysis is quite complex and we are a long way from being able to predict outcomes, especially since environment plays a role. What we do know is that as long as different environmental zones exist, different phenotypes will exist. This means, some sci-fi stories to the contrary, that we will not all end up looking similar as we mate together more with those whose phenotype differs from our own. The more probable outcome is to increase phenotypic diversity. This is good since it provides more variability in the human population and increases the chances that there will be individuals who will be able to survive environmental changes.
2.2 Darwin Triumphant
K.I. Dawkins posits that the truths that Darwin discovered are more universal truths than those of Freud or Marx. The truths of Freud and Marx pertain to certain historical circumstances, but cannot generalize to all of biological science.
Creationists may use the Second Law of Thermodynamics—that everything moves toward Entropy—to argue against the validity of Darwinian evolution. How could increasingly complex beings be created? The answer is that evolution gave rise to organisms better and better equipped to survive and reproduce. Those who reproduced the most would “win” and become a most populous species. Mutations are random, BUT the way in which they interact with the environment to encourage or discourage survival are non-random.
It is relevant to ask whether this is happening today to the earth. Humans rule, as the dinosaurs once did. Humans have been very successful in reproducing and their numbers are skyrocketing. The result is that many species are being wiped out by human hands. Half the earth’s species are projected to disappear by the end of the 21st century, the result primarily of human activity and human alteration of the earth’s climate through global warming. Humans could even be thought of as “parasitic” beings with respect to the balance of the ecosystem.
K.F. In discussing the Second Law, Dawkins points out that this law refers to a closed system and life on earth, as long as the sun continues to shine, is not a closed system. He then uses a helpful analogy to distinguish how evolution operates as opposed to a purely random system. A library without a process in place to make sure books are returned to their proper places on the shelves will become unusable and chaotic. That would be a randomness. Fortunately for life on earth, there is a process in place that allows for increasing order and complexity. That process is natural selection. At any given point in time there are certain environmental constraints. Individuals who are best adapted to those particular constraints are the ones who will be most likely to survive to reproductive age, to reproduce, and to pass on their genes. Natural selection is not a random process, but it is a slow and gradual one. Under a given set of constraints, large genetic changes (mutations) are unlikely to be adaptive. The most probable outcome is that the individual will be selected out of the population. “Adaptive evolution must in general be a crawl through genetic space, not a series of leap.” [p. 86]
2.3 The ‘Information Challenge’
K.F. This section will be of great interest to the computer techies out there. Dawkins does an excellent job of explaining how DNA is digital. Because of this, we can easily compare genes between different organisms and can determine the time span since they last shared a common ancestor. DNA is information. The genome of a species encodes the history of that species and records the adaptive changes over time that allowed the species to survive to this point. “Information from the ancestral past can be seen as a manual for surviving in the present: a family bible of ancestral ‘advice’ on how to survive today. We need only a little poetic license to say that the information fed into the modern genomes by natural selection is actually information about ancient environments in which ancestors survived.” [p. 103]
2.4 Genes Aren’t Us
K.I. The popular press often comes out with headlines about a gene specific for a condition, for example a “gay gene” is discovered. Other examples are a gene for depression, a gene for alcoholism, a gene for intelligence. The title, “Genes Aren’t Us” emphasizes that genes cannot determine our behavior. Our behaviors, like other genetic traits, are almost always multifactorial, depending on the interaction of numbers of genes on different chromosomes. Furthermore, environmental factors greatly modify genetic ones. So intelligence, homosexuality, and other traits may be at least 50% environmental.
Recently, an article came out about the biochemical environment affecting male babies with regard to the tendency to become gay males (featured in Wall Street Journal, June 30 or so). It seems that if a boy had an older brother or brothers, he is more likely to be gay than a boy with older sisters. That is because the presence of a male gestation is thought to cause maternal antibodies against the Y chromosome. Antibodies cross the placenta, so the Y chromosome in males of subsequent gestations somehow gets targeted for damage by these antibodies and the damage is thought to predispose to homosexuality.
So, environmental factors can start to affect behavior even in utero.
K.F. While behaviors and personality have a genetic base, this does not mean that they are genetically determined. It does mean there are limits to how much they can be modified by the environment, both in utero and ex utero. It is improbable that someone who is withdrawn and reserved will become gregarious and voluble. But, with concerted effort, she may be able to become somewhat more outgoing.
2.5 Son of Moore’s Law
K.I. The discovery of the intricacies of modern molecular genetics is a truly great achievement, and as a basic science researcher myself I appreciate the ongoing greatness of the discoveries. For instance, the expression of a gene is governed by DNA sequences called promoters. These promoters determine whether or not a gene is going to make a protein or remain inactive. Then, there are large expanses of wasted DNA with “pseudogenes” that are genetic junk, or vestigial but their presence shows the interconnectedness of species.
The genetic material is “digital” with gigabases being like gigabytes on a computer chip. In fact, a lot of the advances being made in modern genetics are with the aid of computers. There are computer programs that will design a sequence of DNA for a desired purpose. And, there are computer analyses being done of genes that are thought to cause susceptibility to diseases such as prostate cancer.
K.F. “Moore’s Law states that computer power doubles every eighteen months.” [p.108] Since DNA is digital, the sequencing of which has been computerized, Dawkins created Son of Moore’s Law which states that every 27 months, the cost to sequence DNA is halved. As costs drop, more and more organisms will be sequenced. Soon we will be able to see how truly interconnected all life is.
Once again, thank you, Dr. Iczkowski. Next month we will review Part 3: The Infected Mind.
AnthroHealth Tip of the Month: It is summer. It is hot. Ice cream and smoothies sound enticing. But eating them frequently doesn’t do a body good. This is the time to focus on fruit: fresh or frozen. Fruit satisfies the sweet tooth without damaging the calorie budget. Even better, fruits are a plentiful source of the nutrients and antioxidants our bodies need to maintain good health. So, pick a plum for summer eating pleasure. Yummm…
Copyright
© 2001-2009 Kathleen E. Fuller, PhD. All rights reserved.
