Questions About Human Evolution

Were you planning on talking about Darwin in your talk about evolution? (And various other broad questions about evolutionary theory)
No--there's not time in one lecture to trace the history of this field of study: we needed to get right on to modern views of evolution. For more information, see Evolution: Theory and History.

How far back in time can we date bones or skeletons?
In the study of human evolution, we actually date the fossils of bones, not the bones themselves. These are mineral deposits that have filled in the space left by the now-decayed bones. If organic material is still present, methods based on the known rate of decay of certain radioactive elements can be used. Carbon 14 dating goes back only 60,000-100,000 years ago, but even in inorganic materials the fission-track and potassium-argon methods can take us back to the origins of life millions of years ago.

More often, however, stratigraphy is used. If the fossils are found buried in a layer (stratum) of soil, then what we do is try to date other items in that same layer by various methods. With enough cross-checking, we can be fairly sure that the fossils belong to the same period. There is always a lot of more-or-less hedging in this sort of dating; but the more of it we do, the clearer the picture becomes. Much stratigraphic work has been confirmed in recent years by studies charting the rate at which genes mutate. If you want to know more about this sort of thing, there are lots of good books in the library on evolution, but an introductory archeology textbook might be a good place to start.

How did certain species of man (e.g. Neanderthal) just "die off"?
There are various theories. Some think Homo Sapiens killed them off. Some think they couldn't survive some disease or other change in their environment. Some think Homo Sapiens interbred with them and proved more hardy. There were never a whole lot of Neanderthals in existence--it wouldn't have taken that much competition from a smarter and healthier group to wipe them out.

What was the manner of their communication?
We just don't know how or when language evolved. It is highly probable hominds had some sort of language before homo sapiens evolved, but we have no direct evidence.

Isn't it true that humans didn't begin to have dental cavities until they started cooking their meat?
Such claims are often made by vegetarians, but I don't know how well founded they are.

I would like to know more about the Ice Man.
Nova (PBS) has a good site on ice mummies. See also Plants and the Iceman.

I'd like to know more about developing skull size in the mother.
Do you mean the decrease in dimorphism between males and females in early hominids? See Sexual Dimorphism as Evidence of Heterochronic Patterns. One related topic is that the increasing size of human skulls caused problems for mothers--bearing children became increasingly difficult. The pelvis could be widened only so much and still allow for women who could run well. So human children are born with small skulls that need a long time to mature, making them much more dependent on their parents for a longer time than most mammals. The soft spot on a newborn baby's head is another way to help get that big head out the birth canal safely.

How smart were Neanderthals and previous species of humans? Is there anything that distinguishes our brains now from the first sapiens sapiens? What if one of the 1st Homo sapiens was put in the school systems of today? Is it our technology that makes us as smart as we are?
We know the Neanderthals could make and use tools and weapons in a manner much more complex than any living ape--so they were definitely brighter than chimpanzees. They made and wore clothes, buried their dead, and used fire. Neanderthals were a variety of Homo sapiens ("smart humans"), so they were actually pretty intelligent. Once you have Homo sapiens sapiens emerging from the Cro-magnons, however, they don't get any smarter. They just think about different things. A normal infant Cro-magnon raised in America today would probably do just fine at WSU. Some people would say our technology actually makes us stupider, but that's another question.

How did there get to be so many different types of people?
This is a big subject, and depends a lot on what you mean by "types." In one sense, we are all the same type (species) since any fertile human can potentially breed with any fertile human of the opposite sex. That's what defines a species. In that sense we are all one.

We are coming to recognize that the old labels we call "race" are pretty superficial. People with similar skin color can be very different genetically in other ways that may be more significant for their health or adaptibility to certain environments than the way they look. There is far more genetic diversity among the peoples of East Africa, for instance, than there is among white Europeans generally.

But human groups vary because there is constant variability built in to our reproductive systems. Not only do different parents provide different combinations of genes, but spontaneous mutations (caused by chemicals, radiation, etc.) produce new genetic variations which can then be passed on. When these variations prove to be "successful" (advantageous in a particular environment) or just happen to be linked to other genetic traits that are useful, they tend to survive and get passed on: but only within the circle of people mating with each other.

If somebody in Siberia happened to develop a great gene for dealing with snow blindness it's not very likely that it would have found its way 50,000 years ago to Turkey. Once a set of genes develops among an isolated population, it tends to stablize unless they begin mating with people outside their group/region. But since the Siberians migrated across Beringia to the Western Hemisphere, it's not surprising that they are a close genetic match to Native Americans.

Where does the missing link come in or is there one?
Well put. Evolution often works through gradual shadings of one genetic configuration into another. Because there was always a very small population of hominids at any given time in distant past it is very unlikely that we would find an example of each step from our ape-like ancestors to modern humans. We are lucky to have the abundance of fossils we do. Every time a new fossil is found which fills in a gap in the sequence we have found a "missing link"--but one can always insist on more and more links. This is a variation on one of the Greek philosopher Xeno's paradoxes, who said that no matter how precisely you measure the position of an arrow in flight, between one point and another you can always imagine another intermediate point. Scientists don't use the term "missing link." This is a bit of biased vocabulary from the 19th century used by opponents of evolutionary theory who trusted that scientists would fail to find enough links in the chain of evidence to link us with our prehuman ancestors. In the sense that there can never be a wholly unbroken chain, they are right; but in the sense that we have lots more links now, and the evidence overwhelmingly favors the evolution of apes and hominids from a common ancestor, they have been outdated by science.

It's worth noting that many modern evolutionary scientists believe that evolution proceeds through large leaps at times, not always by the terribly slow accumulation of small changes that Darwin thought were necessary. Knowledge of how genes change has transformed much of our understanding of evolution. We can actually watch evolution take place in simple organisms like the Human Immunodeficiency Virus (the virus that causes AIDS). Evolution is an phenomenon observable in the lab these days, though only in very rapidly reproducing simple living forms. Larger, more complex organisms take longer--though not always as long as you might think.

Where did the word evolution come about?
It was first used in the mid-17th century in England, meaning "developing," but derived from roots meaning "opening out," "unfolding." It literally has to do with something coming out of its envelope. It was quickly applied to various kind of developmental change. People spoke of "the evolution of an idea" in the 19th century. Individual plants and animals were spoken of as evolving from one stage to the next before Darwin adopted the term to describe the emergence of new forms of life in 1859.

Will there ever be enough evidence to completely prove the theory of evolution?
That depends on what you consider "proof." In non-scientific English we speak of something being "just a theory" and contrast theories with facts. That's not scientific usage. The theory of evolution is as well established among scientists as the theory of gravity is among physicists. In science a theory is an explanation (what people mean when they say "just a theory" is what scientists call a hypothesis), and evolution is universally accepted among biologists as the explanation for the living world as we see it. The only biologists who reject it are people whose religious beliefs conflict with evolution. Because their objections are ultimately based on faith, no amount of logical demonstration or evidence is likely to change their minds.

Why doesn't this course give equal time to creationism?
What is called "scientific creationism" is an attempt by certain modern conservative Christians to reconcile the creation story in the Bible with science, but it is not accepted by non-fundamentalist biologists. There is no controversy within biology that evolutionary theory explains how humans and other life forms evolved, though scientists constantly debate the details. The only advocates of creationism within biology are people whose religious beliefs move them to resist the standard explanations.

The American public often imagines that evolution is on shakier ground than it really is because of the vociferous arguments by creationists that are simple and easy to grasp whereas scientists are reluctant to enter into debates with people they consider non-scientists. They are a lot like astronomers who just sigh when you ask them about astrology. It takes a considerable amount of serious study to understand how evolution works, and "equal time" gives an unfair advantage to arguments that scientists consider deeply flawed, though easy to understand. Public schools, afraid of controversy, mostly avoid teaching about modern evolutionary theory; so the general public does not have the knowledge it needs to understand even the basics. The result is that the U.S. is the only Western industrialized nation in which the majority of the population rejects a belief in evolution.

Some of you may have taken courses aimed at contrasting evolutionary theory with "creationism." Such courses commonly present at best a heavily filtered view of evolution. To get a good grasp of what those who work on a daily basis with the subject base their ideas on we need to encounter them on their own turf, unfiltered by editors trying to discredit them, before comparing them with creationists. Until we've done that, we can't really say we've given evolution a fair hearing.

Modern biology, geology, and many related sciences build on evolutionary theory as their core. If you would like explore evolution seriously, I highly recommend Zoology 150: Evolution.

Here's a hint in following this sort of debate. Whenever you hear someone ridicule scientists by presenting an argument that is simple and easy for nonspecialists to follow but which the person making it insists is ignored by scientists, you can be fairly certain that you are not getting the whole story. Scientists sometimes make mistakes, but not usually the grossly stupid ones that creationists accuse them of.

For detailed answers to various creationist arguments, please see The Talk-Origins Archive.

If you believe that your religious faith precludes belief in evolution, that need not affect your performance in this class. We do not ask that you accept as true all the beliefs and theories we present here--you just need to know about them. So long as you are able to state on exams what evolutionary theory says you should be fine--you don't have to agree with it.

Many deeply religious people accept evolutionary theory. Even the Pope has announced that it does not conflict with Catholic doctrine, and that to believe in it is not contrary to faith.

The library has lots of good books on the subject. Here are the recommendations of the Encyclopedia Britannica:

The history of evolutionary theories from Darwin to the present is traced in Ronald W. Clark, The Survival of Charles Darwin: A Biography of a Man and an Idea (1984, reissued 1986), which also presents an engaging biography of Darwin. The most authoritative historical treatise of evolutionary ideas from antiquity to the present is Ernst Mayr, The Growth of Biological Thought: Diversity, Evolution, and Inheritance (1982). Ernst Mayr and William B. Provine (eds.), The Evolutionary Synthesis: Perspectives on the Unification of Biology (1980), contains historical articles by several of the great evolutionists who formulated the synthetic theory.

Modern treatments of evolutionary theory include G. Ledyard Stebbins, Darwin to DNA, Molecules to Humanity (1982), a readable discussion providing coverage of human evolution, both biological and cultural. A fairly comprehensive text requiring only general biology as background is Francisco J. Ayala and James W. Valentine, Evolving: The Theory and Processes of Organic Evolution (1979). A more advanced text is Theodosius Dobzhansky et al., Evolution (1977). Francisco J. Ayala, Population and Evolutionary Genetics: A Primer (1982), provides an introduction to the genetics of the evolutionary process. A more advanced and mathematically demanding work is Philip W. Hedrick, Genetics of Populations (1983, reissued 1985). The origin of species is the subject of Michael J.D. White, Modes of Speciation (1978); and of the more comprehensive Ernst Mayr, Animal Species and Evolution (1963), which is a classic work. G. Ledyard Stebbins, Flowering Plants: Evolution Above the Species Level (1974), discusses plant speciation and evolution.

A good introduction to the fossil record is a collection of articles from Scientific American, edited by Léo F. Laporte, The Fossil Record and Evolution (1982). George Gaylord Simpson, The Meaning of Evolution: A Study of the History of Life and of Its Significance for Man, 2nd rev. ed. (1967, reissued 1971), is written for the general reader yet is an authoritative work dealing particularly with paleontological principles and the evolutionary process through time; somewhat more technical is his Major Features of Evolution (1953, reprinted 1969). An authoritative treatise on paleontological principles is Stephen Jay Gould, Ontogeny and Phylogeny (1977).

Two good introductions to molecular evolution are Francisco J. Ayala (ed.), Molecular Evolution (1976); and Masatoshi Nei and Richard K. Koehn (eds.), Evolution of Genes and Proteins (1983). The neutrality theory is presented in full by its main theorizer in Motoo Kimura, The Neutral Theory of Molecular Evolution (1983); and the theory that evolutionary changes happen not gradually but abruptly is advanced by one of its originators in Niles Eldredge, Time Frames: The Rethinking of Darwinian Evolution and the Theory of Punctuated Equilibria (1985).

Stephen Jay Gould is a leading evolutionary theorist (despite being selectively quoted by enemies of evolution to present him as some sort of anti-evolution figure) who has written many engaging books for the general public on the topic. Especially recommended for beginners is a book he helped edit, The Book of Life: An Illustrated History of the Evolution of Life on Earth. It is in Owen Science Library (call number QH325 .B65 1993).

A good, though somewhat dated, overview of scientific views of human evolution is the six-part video series, The Making of Mankind, based on the work of Richard Leakey (VHS 16286-16291). The new PBS series Evolution is a little short on detail, but gives a highly dramatic overview of the subject (VHS 19830, vols. 1-8). The first episode on Darwin is particularly good. It does not explore the fine points that would convince an open-minded disbeliever, however.


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