lecture 8 - evolution of a cognitive brain Flashcards

Question

competition

Answer 1

* The second aspect of natural selection is competition. Individuals of a given species share a similar environment. Because of this, competition within a species for food, mates and territory is inevitable. Every fish captured and eaten by one bald eagle is a fish that cannot be captured and eaten by another bald eagle. If one bald eagle finds a suitable mate, then there is one fewer potential mate for other bald eagles, and so on. * Competition also occurs between species when members of different species vie for similar ecological resources, such as food and territory. * Competition for other resources indirectly influences reproductive success because the ability to find and court a suitable mate depends on the ability to stake out and defend a territory having an adequate food supply. The probability of a yellow-headed blackbird finding a mate and successfully rearing a family depends not only on its success in competing against other yellow-headed blackbirds, but also on its success in competing against red-winged blackbirds. * Natural selection works because the members of any species have different phenotypes. Because these phenotypes are caused by different genotypes, successful individuals will pass on their genes to the next generation. Over time, competition for food and other resources will allow only the best-adapted phenotypes (and their corresponding genotypes) to survive, thereby producing evolutionary change. This is what the theory would predict.

Answer 2

* In the US, it is law that science and religion are taught separately and that banning the teaching of evolution is unconstitutional (Scott and Matzke, 2007). * In 2007, the Council of Europe’s Parliamentary Assembly passed a resolution recommending that member states do not teach creationism as if it were the equivalent of science. * Creationism – the rejection of the theory of evolution in favour of the belief that the world was originated by a Creator – has gained some momentum in the USA, although recent legal rulings suggest that evolution is fighting back. Creationism’s new incarnation is Intelligent Design but, to all intents and purposes, the terms are synonymous. * Every year since 1985, the inhabitants of the US have been asked about the theory of evolution and whether they agree with it. In 2019 and 2020, 40 per cent and 54 per cent of people respectively accepted the theory of evolution (Miller et al, 2021). * Miller et al also identified some predictors of this acceptance: younger people were slightly more likely to accept evolutionary theory, more men than women were, as were people who had completed 10 or more years of college (the strongest predictor). There has been a steady increase in the US of people attaining higher levels of education; the percentage of adults with baccalaureate qualifications, for example, was 20 per cent in 1988 but 35 per cent in 2018. * Religious fundamentalism, perhaps not surprisingly, was correlated with non-acceptance over 30 years of the survey. There was also a political division: in 2019, 83 per cent of liberal Democrats accepted the theory of evolution; 34 per cent of conservative Republicans did. The second highest predictor of acceptance was scientific literacy which may be explained by the increase in people taking mandatory science courses at college.

Answer 3

* Reconstruction of human evolution is a difficult job, something akin to assembling a giant jigsaw puzzle whose pieces have been scattered throughout the world. Some of the pieces may have been lost for ever; others have become damaged beyond recognition; and those few that are found force continual reinterpretation of how the other pieces might fit the puzzle. * Another way in which we can date our remains is via carbon dating. Animals breathe a form of (naturally occurring) radioactive carbon called C-14. When an animal dies, this carbon decays but at a constant rate. By examining the content of the carbon in the fossil or surrounding material, therefore, we can estimate the date of its existence. * One problem here is that the amount of carbon found can be influenced by the amount in the air at the time. * We can also analyse the changes in DNA between similar fossils – the less the change in DNA, the closer the two fossils are in time. But the best we can do is to make an educated guess about the evolution and lifestyles of our ancestors. * Many biologists and natural historians of Darwin’s time believed that natural selection applied to all animals, including humans. Others insisted that although natural selection applied to other animals, it did not apply to humans. However, through study of the fossil record and recent developments in genetic research, we now know that our species is related genetically to other mammals. The gorilla and the chimpanzee are our closest living relatives, and together we appear to have descended from a common ancestor. You may have heard it said that we share 99 per cent of our genes with chimps. In fact, what we share is DNA involved in the production of proteins. Ninety-nine per cent of our DNA in this regard is identical (King and Wilson, 1975).

Answer 4

The reason is that 98 per cent of the human genome is not involved in the production of proteins. * The remainder is involved in the timing of production and how much is produced (these are called regulatory genes – there is a more detailed description of genetics later in the chapter). * It is this percentage which causes the great difference between the species (Demuth et al, 2006). Humans also have multiple copies of genes that chimps do not (Pennisi, 2006). Therefore, while we have proteins in common, it is the way in which these proteins are organised that determines the differences between us. * Our dependence on information from fossil remains and other archaeological artefacts is problematic. As Byrne (1995) has colourfully pointed out, much of what we conclude about our ancestors’ behaviour from archaeological findings is speculative; some is sensible speculation, but it is speculation, nonetheless. * There is no way of empirically or conclusively demonstrating that artefacts were used in the way in which we suggest or that they indicate a specific way of living or behaving. In this sense, paleoanthropology – the study of human behaviour using information from fossil remains – is more like detective work than scientific work. ‘The reality’, Byrne argues, ‘is that we will never know with confidence the answers to many of the most important questions we would like to ask about what happened in the past five million years’ (1995, p. 6). With this caveat in mind, the general pattern of evolution is thought to occur something like this. Our evolution from a common ancestor appears to have begun in Africa about two to four million years ago (Clark, 1993).

Answer 5

* The earliest humans have been labelled Homo habilis (literally ‘handy man’). Homo habilis was small (only about 1.3 m tall and about 40 kg in weight) but was bipedal (able to walk upright on two feet). Compared with its predecessor – a species called Australopithecus (apes from the South) – Homo habilis had a larger brain and more powerful hands. The strong hands were well suited to making simple stone tools; hence the name ‘handy man’. * A natural selection interpretation of such adaptively significant traits would argue that these early humans adapted to the environment in terms of creating shelter against the elements, catching and preparing food, and making weapons for self-defence. Homo habilis was succeeded, about 400,000 years later, by Homo erectus (upright man). Homo erectus had a much larger brain and stood more erect than Homo habilis and had a more complex lifestyle.

Answer 6

* Homo erectus was the first of our ancestors to establish regular base camps, which probably served as centres for social activities, including the preparation and eating of food. We cannot be absolutely sure that these interpretations are the correct ones, however. Homo erectus created more efficient and stronger tools than did Homo habilis, successfully hunted big game, and discovered and used fire. Fire enabled these early humans to cook food, remain warm in cold weather and protect themselves from predators. Homo erectus’s use of fire, coupled with its apparent social nature and its ability to hunt and/or scavenge big game, permitted it to explore and settle new environments, including Europe, Asia, America and other parts of Africa (Spoor et al, 2007).

Answer 7

* The earliest known Homo sapiens (intelligent man) appears to have arisen about 500,000 years ago. The best known of the early Homo sapiens, Homo sapiens neanderthalensis (so-called Neanderthals, named after the German valley in which the fossils were discovered), lived throughout Europe and Central Asia between approximately 300,000 and 35,000 years ago. * Neanderthals constructed small huts from bones and animal skins and sometimes burned bones as fuel. They were skilled big game hunters, tool makers and clothiers, and they had cultural rituals for burying their dead. * In one Neanderthal burial site unearthed in France, a small boy was found positioned on his left side with a small pillow of flints under his head and an axe positioned by his right hand. * Similar Neanderthal burial sites have been discovered, suggesting that these humans possessed cultural traditions not previously found in the prehistoric record. * Informed speculation suggests that Neanderthals and modern humans (Homo sapiens sapiens) overlapped each other, although the origin of Homo sapiens sapiens is unclear. It seems to have arisen between 200,000 and 100,000 years ago. * The Neanderthals became extinct around 25,000 years ago, with last evidence of their existence found in Gibraltar (Finlayson et al, 2006). What is clear, though, is that the Homo sapiens sapiens line has survived to flourish in all parts of the world, despite the presence of hostile climate, terrain and predators. Some theorists have suggested that the variety of species is greater nearer the equator (Hillebrand, 2004) and that tropical environments create a museum and a cradle for species to flourish (McKenna and Farrell, 2006).

Answer 8

* The apparent success of the human species in adapting to a variety of ecological niches stems from the fact that natural selection has favoured two important human characteristics: bipedalism, the ability to move about the environment on two feet, and encephalisation, increased brain size. * The ability to walk upright, which appears to have evolved in our early hominid ancestors over 4 million years ago (Boaz, 1993; Ruff et al, 1997), may have arisen from the need to stand on branches to reach food on other branches above (Thorpe et al, 2007). Bipedalism allowed not only greater mobility, but also freed the hands for grabbing, holding and throwing objects. * The ability to grasp objects, in combination with an expanding capacity for learning and remembering new skills provided by a larger brain, led to advances in tool making, food gathering, hunting and escaping predators (Eccles, 1989). * Early hominids had a brain volume of 650 cm3 (and they were about 155 cm tall). Current humans have a brain size of 1,500 cm3 and are, on average, 175 cm tall. It used to be thought that there was a relationship between body size and brain volume. However, the relationship is between relative size and brain volume. * The increase in our brain relative to our size is called positive brain allometry. This began around 2 million years ago and has increased since – from 1,000 cm3 (Homo habilis) to (Homo erectus) to 1,350 cm3 100,000 years ago 450 cm3 (Homo sapiens). The increase may be attributable to better diet, better defence and, therefore, better survival. Children began to live longer, thus enabling the brain to be more fully developed. The increase in brain volume is thought to be the result of increased surface area of the brain (the neocortex), but also the development of a structure near the brain stem, the cerebellum (Miller et al, 2022).

Answer 9

by Smaers et al’s analysis of 107 extinct species and 1311 extant species spanning 21 orders. They examined where and when the shift in allometry happened and explored whether this was driven by brain size or by body size; that is, was a larger brain required for a larger body or did a larger body lead to a larger brain. They found that there were shifts in the slope of relative brain size. * Changes in brain/body allometry seemed important for the diversification of mammalian species in the Cretaeous–Pateogne period, but the slope increased and decreased with later diversification. * They highlight the curious case of the polar bear and the Californian sea lion; their mean body size is similar, but the brain of the polar bear is twice as large. The sea lion, however, has 3–6 times more volume in brain regions required for cognition. “Cognitive tests in polar bears,” they write, “are generally lacking” (p. 6). They suggest that rather than focusing on brain volume, it may be more informative to examine relative regional brain volume. * As the brain became larger, more of its volume – especially the front part which is the most recently evolved – appeared to become devoted to thinking, reasoning, decision-making and other complex cognitive, ‘higher’ functions. Genetic studies (GWAS) have identified over 100 genetic loci responsible for variability in human cortex (Grasby et al, 2020). Tilot et al (2021) attempted to determine the genomic changes that occurred by analysing surface area from 33,000 humans and how these were associated with genes. There was evidence of gene selection leading to increased surface area of the brain over 2000–3000 years and one specific gene selecting for the inferior frontal gyrus, the speech area.

Answer 10

the ability to anticipate future events and to consider the effects of these events on an individual or group of individuals. Such planning might have involved the organisation of hunts, the institution of social customs and events (such as weddings and funerals), and the planting and harvesting of crops. * Over time, the interaction between bipedalism and encephalisation allowed humans to exploit new environments and establish well-organised communities. * Advances in tool making and hunting, combined with the use of fire for cooking, protection and warmth, were adaptive: they helped humans to live longer. * The increased lifespan of humans may have aided the gradual accumulation of wisdom as the older members of early human communities began to share their knowledge with younger members through language. * Although the fossil record cannot tell us when language first developed, we assume that those who were able to communicate with others through language had a distinct advantage over those who could not. Language originated and subsequently evolved because of its immensely adaptive significance (Pinker, 1994). As Skinner (1986) noted, language not only provided a simple means of warning others of danger, but also provided a means of communicating important information to others, such as the location of a good hunting spot or instructions on how to craft a tool. Perhaps the most important advantage conferred by language was its ability to reinforce the already strong social tendencies of early humans. Language is the foundation upon which all human cultures are built

lecture 8 - evolution of a cognitive brain Flashcards

(34 cards)