1. Mental decline with age is caused by loss of neurons.
2. Healthy aging is accompanied by a considerable loss of memory.
3. Nerve cells can both age and regenerate with time.
4. Neurons respond very slowly to the change of environment and lifestyle.
5. Age can bring some improvement of mental activity.
Exercise 8. Summarize all the information about age-related transformations in the human organism discussed in this unit and speak on aging and the current research in this sphere.
Unit 15. Food
Then I commended mirth, because a man hath no better thing under the sun, than to eat, and to drink, and to be merry.
One should eat to live, not live to eat.
There is no love sincerer than the love of food.
George Bernard Shaw
Exercise 1. What do you know about food?
1. What nutrients are necessary for human life?
2. Why are vitamins and minerals necessary?
3. How much food should people consume? What does the daily norm of food consumption depend on?
4. What is generally understood as “healthy diet”?
5. What food products are considered healthy and unhealthy? Why?
6. What factors can lead to overweight and obesity?
7. What role have dietary habits played in human evolution?
8. How did cooking food affect human physiology?
Exercise 2. The article below deals with the role of dietary habits in human evolution. As you read the text, find answers to the questions:
- What were the main dietary shifts in human evolution?
- What changes have they led to?
Food for Thought
Dietary change was a driving force in human evolution
By William R. Leonard
We humans are strange primates. We walk on two legs, carry around enormous brains and have colonized every corner of the globe. Anthropologists and biologists have long sought to understand how our lineage came to differ so profoundly from the primate norm in these ways, and a growing body of evidence indicates that these miscellaneous quirks of humanity in fact have a common thread: they are largely the result of natural selection acting to maximize dietary quality and foraging efficiency. Changes in food availability over time, it seems, strongly influenced our hominid ancestors. Thus, in an evolutionary sense, we are very much what we ate.
So when and how did our ancestors’ eating habits diverge from those of other primates? Further, to what extent have modern humans departed from the ancestral dietary pattern?
To appreciate the role of diet in human evolution, we must remember that the search for food, its consumption and, ultimately, how it is used for biological processes are all critical aspects of an organism’s ecology. The energy dynamic between organisms and their environments-that is, energy expended in relation to energy acquired-has important adaptive consequences for survival and reproduction. The type of environment a creature inhabits will influence the distribution of energy into maintenance energy (which keeps an animal alive on a day-to-day basis) and productive energy (which, on the other hand, is associated with producing and raising offspring covering the increased costs that mothers incur during pregnancy and lactation). Thus, by looking at the way animals go about obtaining and then allocating food energy, we can better discern how natural selection produces evolutionary change.
Without exception, living nonhuman primates habitually move around on all fours, or quadrupedally, when they are on the ground. Scientists generally assume therefore that the last common ancestor of humans and chimpanzees (our closest living relative) was also a quadruped. Exactly when the last common ancestor lived is unknown, but clear indications of bipedalism-the trait that distinguished ancient humans from other apes-are evident in the oldest known species of Australopithecus, which lived in Africa roughly four million years ago. Ideas about why bipedalism evolved abound in the paleoanthropological literature. C. Owen Lovejoy of Kent State University proposed in 1981 that two-legged locomotion freed the arms to carry children and foraged goods. More recently, Kevin D. Hunt of Indiana University has posited that bipedalism emerged as a feeding posture that enabled access to foods that had previously been out of reach. Peter Wheeler of Liverpool John Moores University submits that moving upright allowed early humans to better regulate their body temperature by exposing less surface area to the blazing African sun.
The list goes on. In reality, a number of factors probably selected for this type of locomotion. My own research, conducted in collaboration with my wife, Marcia L. Robertson, suggests that bipedalism evolved in our ancestors at least in part because it is less energetically expensive than quadrupedalism. Our analyses of the energy costs of movement in living animals of all sizes have shown that, in general, the strongest predictors of cost are the weight of the animal and the speed at which it travels. What is striking about human bipedal movement is that it is notably more economical than quadrupedal locomotion at walking rates.
For hominids living between five million and 1.8 million years ago, during the Pliocene epoch, climate change spurred this morphological revolution. As the African continent grew drier, forests gave way to grasslands, leaving food resources patchily distributed. In this context, bipedalism can be viewed as one of the first strategies in human nutritional evolution, a pattern of movement that would have substantially reduced the number of calories spent in collecting increasingly dispersed food resources. Indeed, modern human hunter-gatherers living in these environments, who provide us with the best available model of early human subsistence patterns, often travel six to eight miles daily in search of food.