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However, in both studies, Wood and colleagues added another test that reminds us to be cautious when interpreting any finding about sex differences in the brain. Instead of simply dividing their subjects by biological sex, they also gave each subject a test of psychological “gender:” a questionnaire that assesses each person’s degree of masculinity vs. femininity—regardless of their biological sex—based on their interests, abilities and personality type. And in both adults and children, this measure of “gender” also correlated with SG size, albeit in just as complicated a way as the correlation between “sex” and SG size. (Larger SG correlated with more feminine personality in adults but less feminine personality in children.)

In other words, there does seem to be a relationship between SG size and social perception, but it is not a simple male-female difference. Rather, the SG appears to reflect a person’s “femininity” better than one’s biological sex: women who are relatively less feminine show a correspondingly smaller SG compared to women who are more feminine, and ditto for men.

This finding—that brain structure correlates as well or better with psychological “gender” than with simple biological “sex”—is crucial to keep in mind when considering any comparisons of male and female brains. Yes, men and women are psychologically different and yes, neuroscientists are uncovering many differences in brain anatomy and physiology which seem to explain our behavioral differences. But just because a difference is biological doesn’t mean it is “hard-wired.” Individuals’ gender traits—their preference for masculine or feminine clothes, careers, hobbies and interpersonal styles—are inevitably shaped more by rearing and experience than is their biological sex. Likewise, their brains, which are ultimately producing all this masculine or feminine behavior, must be molded—at least to some degree—by the sum of their experiences as a boy or girl.

And so, any time scientists report a difference between male and female brains, especially in adults, it begs the question, “Nature or nurture?” Is women’s larger SG the cause of their social sensitivity, or the consequence of living some 30 years in a group that practices greater empathetic responding? Wood and colleagues are among the few neuroscientists to analyze male-female brain differences for their relationship to gender type, as opposed to strict biological sex. Their findings do not prove that social learning is the cause of male-female differences in the brain, but they do challenge the idea that such brain differences are a simple product of the Y chromosome. (From Scientific American Online, September 8, 2009)

Exercise 6. Answer the questions using the information from the text:

1. Why is social cognition regarded a fruitful area of investigation?

2. What is nature/nurture dilemma?

3. What is straight gyrus (SG) and what is it responsible for?

4. How do researchers explain larger SG in women from the evolutionary perspective?

5. How did the results of the second study contradict those of the first?

6. What correlation between SG size and sex/gender was finally established?

7. How can it be interpreted?

Exercise 7. Divide into two groups. Each group should read either Text A or Text B about differences between the sexes. Then tell other students what you have read about.

Text A. Enzyme Lack Lowers Women's Alcohol Tolerance

By Harald Franzen

An international team of researchers may have found one of the reasons why alcohol harms women more than men: women, it appears, are deficient in an enzyme that helps metabolize alcohol. The findings appear in the April issue of Alcoholism: Clinical and Experimental Research. "It has been known for a long time that, in general, both women and female animals are more susceptible to the negative or toxic effects of alcohol," team member Steven Schenker of the University of Texas at San Antonio says. "This is true for the liver, heart muscle and skeletal muscle, and it may be true for the pancreas and the brain. In other words, there is something about the female gender that makes them more susceptible to toxic amounts of alcohol."

In the past scientists attributed this susceptibility to women's smaller body size and their relatively higher percentage of fatty tissue. For this study, however, the researchers focused on what is known as first-pass metabolism. Before alcohol reaches the blood stream, it goes through the stomach, where so-called gastric alcohol dehydrogenase (ADH) isozymes break some of it down. "In an earlier study we found that women have less of this ADH activity than men do," notes lead author Charles Lieber of the Mount Sinai School of Medicine. "Accordingly, women have a lesser first-pass metabolism and, therefore, for a given dose of alcohol, their blood level is higher than it is for men."

Following up on that research, the team recently turned their attention to the makeup of ADH. They found that one of the enzyme's three components, glutathione-dependent fomaldehyde dehydrogenase (x-ADH), is deficient in women, thus explaining their lower ADH activity levels. To Schenker, the take-home message is clear: "Women simply need to be more cautious than males in terms of the amount of drinking they do." (From Scientific American Online, April 16, 2001)

Text B. Data Trends Suggest Women Will Outrun Men in 2156

By Sarah Graham

Every four years, athletes from around the world travel to the Olympic Games to compete in the 100-meter dash, hoping to earn title of fastest man or woman on Earth. A new statistical analysis suggests that in the year 2156, the winner of the women's event may finally outrun her male counterpart.

Andrew J. Tatem of the University of Oxford and his colleagues collected the finishing times in the men's 100-meter dash run in 1900 and from 1928 (when the women's race was first run) to 2004. The winning times for both genders have been steadily decreasing, with female competitors improving at a slightly faster clip than the males. By plotting the results against the year of competition and extrapolating the results, the team determined that the fastest human on the planet could be a woman after the 2156 games. In today's issue of the journal Nature, they report with a 5 percent margin of error that the event could take place as soon as 2064 or as late as 2788, however.

Tatem is the first to admit that the study represents a purely academic exercise. A disease researcher by trade, he says the new study was a result of noticing a strong and interesting trend in sprinting. Indeed, the relationship was surprisingly linear and no other model fit the data as well. “We decided to throw caution to the wind and see if current trends continued, what would happen in the future,” he remarks. Potential confounding factors that are not addressed in the new analysis include illegal drug use, environmental conditions on race day, national boycotts and timing accuracy. In addition, some researchers contend that humans are hurtling toward the limits of their potential and that the winning times predicted for 2156 (8.079 seconds for the female champion and 8.098 seconds for the male winner) are simply beyond our grasp. The next chance to check the trend comes in 2008 at Beijing. (From Scientific American Online, September 30, 2004)

Exercise 8. Summarize all the information discussed in this unit and speak on the role of the sexes in nature.

Unit 14. Aging

What makes old age hard to bear is not the failing of one’s faculties, mental and physical but the burden of one’s memories.

W. Somerset Maugham

The body is most fully developed from thirty to thirty-five years of age, the mind at about forty-nine.

Aristotle

Exercise 1. What do you know about aging?

1. What is aging?

2. What changes take place in human organism with age?

3. How does aging affect the human brain?

4. Is aging genetically programmed?

5. Can aging be stopped or avoided?

6. Do age-related diseases result from aging?

Exercise 2. Read the article below and find answers to the questions:

1. How does the text define and explain aging?

2. What is the relation between aging and diseases?

3. Do the authors agree that aging is genetically programmed? Why?

No Truth to the Fountain of Youth

What Aging Is... and Isn’t

By S. Jay Olshansky, Leonard Hayflick and Bruce A. Carnes

Any discussion of aging should first clarify its terms. Various definitions have been proposed, but we think of aging as the accumulation of random damage to the building blocks of life—especially to DNA, certain proteins, carbohydrates and lipids (fats)—that begins early in life and eventually exceeds the body’s self-repair capabilities. This damage gradually impairs the functioning of cells, tissues, organs and organ systems, thereby increasing vulnerability to disease and giving rise to the characteristic manifestations of aging, such as a loss of muscle and bone mass, a decline in reaction time, compromised hearing and vision, and reduced elasticity of the skin.

This accretion of molecular damage comes from many sources, including, ironically, the life-sustaining processes involved in converting the food we eat into usable energy. As the energy generators of cells (mitochondria) operate, they emit destructive, oxidizing molecules known as free radicals. Most of the damage caused by these reactive molecules gets repaired, but not all. Biologists suspect that the oxidative assaults ultimately cause irreparable injury to the mitochondria, thereby impeding the cell’s ability to maintain the integrity of the countless molecules needed to keep the body operating properly. The free radicals may also disrupt other parts of cells directly.

Aging, in our view, makes us ever more susceptible to such ills as heart disease, Alzheimer’s disease, stroke and cancer, but these age-related conditions are superimposed on aging, not equivalent to it. Therefore, even if science could eliminate today’s leading killers of older individuals, aging would continue to occur, ensuring that different maladies would take their place. In addition, it would guarantee that one crucial body component or another—say, the cardiovascular system—would eventually experience a catastrophic failure. It is an inescapable biological reality that once the engine of life switches on, the body inevitably sows the seeds of its own destruction.

Men and women in the developed world typically live longer now (75 and 80 years, respectively) than they did throughout much of history (about 25 years) because human ingenuity—which brought us sanitation systems, vaccines, antibiotics and so on—has had phenomenal success in thwarting the infectious and parasitic diseases responsible for a great deal of premature death. We live longer now not because we have altered the way we age but because we have altered the way we live.

Though inevitable, aging is not, as some might think, a genetically programmed process, playing itself out on a rigidly predetermined time schedule. The way evolution works makes it impossible for us to possess genes that are specifically designed to cause physiological decline with age or to control how long we live. Just as an automobile does not have a built-in plan for decline written in its blueprints, we do not possess genetic instructions that tell our bodies how to age or when to die.

The logic behind this assertion goes basically like this: Genes perpetuate themselves by orchestrating the transformation of a fertilized egg into a sexually mature adult that produces offspring. Clearly, any genetic variant that compromises this developmental process would be self-eliminating. Conversely, evolution is totally blind to the consequences of gene action (whether good, bad or indifferent) after reproduction is achieved. Genes or genetic variants that prove detrimental in the postreproductive part of the life span can become commonplace, but only if they participate in important processes early on. For example, several genes that contribute to cancer in the later years are known to participate in growth and development early in life.

Without a doubt, a host of our genes influence aging, but they do so indirectly, as an inadvertent by-product of processes involved in growth, development, and the maintenance of health and vigor. The lack of a specific genetic program for aging and death means that there are no quick fixes that will permit us to treat aging as if it were a disease. A single genetic intervention in an organism as complex as a human being would have little chance of combating the probably vast array of genes and biological activities that play subtle, unpredictable parts in the timing of our ultimate demise. (From Scientific American Online, December 29, 2008)

Exercise 3. You are going to read an article about centenarians – people who are more than 100 years old. Before reading discuss the following questions:

1. Are there any biological limits to human life span?

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