Anthropology For Dummies. Cameron M. Smith
the term selection implies that someone is making a decision, or selecting. But really, it just refers to the survival probability of a given life form. One way to think of selection with less implication of a deliberate “selector” is in the phrase “the organism proposes, the environment disposes.”
Speciation
Sometimes groups of living things move from one environment to another, as when air currents carry insects to a distant island, or some subpopulation of a species of squirrel somehow crosses a river and is cut off from its original population. When this happens, new selective pressures (different temperatures, say, in the new region) may reshape the population so much that if it were to rejoin its ancestral population, the two couldn’t interbreed. This event is called speciation, and it’s what most people think of when they think about evolution: one life form gradually changing into another.
Because speciation can take a long time (anywhere from thousands to millions of years), it’s hard to observe. Still, you can see it in the fossil record, where billions of years of Earth life have left traces of their change through time. And that record speaks clearly, even though it has gaps here and there (because geological forces have wiped out some fossils, for example, or animal and plant remains simply didn’t fossilize due to geochemical factors). All of this tells anthropologists that yes, all living species have long evolutionary histories, including Homo sapiens and all its living and past relatives in the primate order. This is where physical anthropology comes in, to investigate that evolutionary past.
WHY BEING HUMAN CAN MAKE EVOLUTION HARD TO UNDERSTAND
Although the world of biology widely accepts evolution, the topic can be hard to understand for several reasons. Leaving aside deliberate mischaracterization of evolution by those with a religious agenda, I’m talking about how being human itself obscures our view of evolution.
By this I mean that although humans evolve, we do so in some ways profoundly different from other species. For the last 100,000 years our outward, physical bodies haven’t evolved too terribly much; modern human skeletons are essentially indistinguishable from those of 100,000 years ago. And yet humanity has changed a great deal; most of us now live in massive cities, instead of as highly mobile foragers, and most of us eat foods grown on farms rather than hunted and collected from across vast landscapes. So what has changed, and how does it make evolution hard to understand?
What have changed are our minds and the cultures we carry in them. Culture, really, is the mind’s set of instructions for what the universe is like and what you’re supposed to do about it. (You can read about culture in more detail in Chapter 11.) Doing is the crux: We humans evolve proactively, inventing artifacts and cultural practices to survive in new environments, not reactively like every other species. Other species don’t even know they’re evolving through time. Consider the Arctic, which was widely colonized after about 1,500 years ago by people who invented dog sleds, whale-hunting equipment, watercraft, and the snow-house or iglu.
This purposive invention leads us, I think, to see living things the way we see our artifacts: as the finished products of some kind of intent. It’s hard to imagine that some mind didn’t make the elm tree for some purpose, because we ourselves invent and build things for specific purposes. But evolution shows that those things can come to be without any conscious plan or designer. That can be hard to reconcile with humanity’s purposeful tendencies.
More facets of physical anthropology
The evolutionary principles underlying physical anthropology touch everything that physical anthropologists study. In this section, I outline a few of the main fields of physical anthropology; you can read about yet more subfields and discoveries in the other chapters in this part of the book.
Primatology
One specialty of physical anthropologists is the study of living primates, a field called primatology. (Some biologists also study primates, but without expressly looking for what they can teach humanity about itself.) Primatological physical anthropology studies primate behavior, biology, evolution, and anatomy. Each of these fields ties into the other, such that what anthropologists learn about behavior informs — and is informed by — what they learn about biology and so on. For example, you can’t fully understand the anatomy of a species without knowing about its evolution because anatomical characteristics — like a prehensile tail, or new kinds of teeth — don’t just pop up out of nowhere; they accumulate (or vanish) as selective pressures change and shape the organism.
Anthropologists study primate behavior by using the principles of ethology, the study of animal behavior. Although approaches vary, they often emphasize
Observation of the animal in its natural environment for long periods — for example, across seasons and years rather than just a few weeks at a time
Careful consideration of the interplay between behavior, environment, and anatomy, accounting for all that’s known about the species
A search for and explanation of widespread similarities of behavior
A search for and explanation of differences of behavior
Unfortunately, study of many primates in their natural habitats is becoming impossible as primate species become extinct or their habitats are reduced. (You can read more about the peril in which many primate species exist in Chapter 4.) Unfortunately, primatologists must often resort to studying primate species in enclosure settings such as zoos (where their behavior and biology must differ from that in the wild). Considering that humanity has only been doing comparative primatology for a few decades and is only just sketching out an understanding of the living primates, this situation is a real shame.
Paleoanthropology
Paleoanthropology (paleo meaning “old”) specifically studies the human species and its relatives in the ancient past, particularly focusing on the early proto-human species, known as the hominins. (You can check out more on hominins in Chapter 6.) Paleoanthropology is extremely diverse and involves finding ancient human fossils, excavating them (and any artifacts found with them, including stone tools), interpreting the skeletal remains to understand the anatomy, and reconstructing hominin behavior as well as evolutionary relationships. To accomplish all this, most paleoanthropologists have a strong background in the following fields:
Evolution: Because the foundation of biology must be comprehensively