Wow. Wow! I post a few fairly well know points about evolution as a safe first diary on Daily Kos, and go make breakfast. I come back, and it is at the top of the Recommended Diaries list and hundreds of comments and votes are rolling in. Thank you all for your recommendations, comments and questions. A very warm welcome.
There were so many excellent comments, questions and quibbles that I simply could not respond to even a decent fraction of them. So, before I go on to the more provocative thoughts about evolution I was planning to write about today, I decided to spend today's diary on responding to some of the comments from yesterday.
Specifically, there was a great deal of discussion on the use of the words fact and theory, and the differences between the vernacular and scientific meanings of these words. Yesterday I decided against offering specific definition for many of these words, simply because I wasn't sure the readership would stand for a list of definitions. Looking through the comments, it is clear I was mistaken. Today I try to rectify that before going on to less prosaic matters.
- Getting on the same page.
If you will, allow me to start by referring you to
http://en.wikipedia.org/... which does a pretty good job of explaining what science is, and is not. There are some points to quibble with in the article, but reading and understanding this would do a great deal for th science education of most Americans.
- Fact and Theory in Scientific English vs. vernacular
http://en.wikipedia.org/...
says,
In the most basic sense, a scientific fact is an objective and verifiable observation; in contrast with a conjecture or theory, which is intended to explain or interpret facts.[19]
This is the sense that the hundreds of working scientists I know use the word "fact" when discussing science.
That is the sense in which I meant fact when I said that evolution is not a fact. According to the more general definition:
Generally, a fact is something that is the case, something that actually exists, or something that can be verified according to an established standard of evaluation.
evolution is a fact. So are the Himalayas.
Many questioned my usage of the word theory, so this is what I meant by it
In scientific usage, a theory does not mean an unsubstantiated guess or hunch, as it can in everyday speech. A theory is a logically self-consistent model or framework for describing the behavior of a related set of natural or social phenomena. It originates from or is supported by experimental evidence (see scientific method). In this sense, a theory is a systematic and formalized expression of all previous observations which is predictive, logical and testable. In principle, scientific theories are always tentative, and subject to corrections or inclusion in a yet wider theory. Commonly, a large number of more specific hypotheses may be logically bound together by just one or two theories. As a general rule for use of the term, theories tend to deal with much broader sets of universals than do hypotheses, which ordinarily deal with much more specific sets of phenomena or specific applications of a theory.
http://en.wikipedia.org/wiki/Theory#Science
- I don't know squat about theology.
One of the first comments yesterday asked
Does God evolve?
Interpreted directly, this is a question for a theologian, not a scientist. On questions of theology, I am both ignorant and agnostic. That is, I both don't know, and accept that I don't know.
On the other hand, the question can be interpreted as "can our understanding of God be said to have evolved in anything analogous to biological evolution?"
Taken this way, the answer is a resounding yes. Richard Dawkins, who invented the idea of a meme, argues that religions that have traits that make them convert nonbelievers and hold onto believers will tend to increase, at the expense of those that don't do these things. Each religion can be seen as a bundle of traits, and each trait is advantageous, disadvantageous or neutral. Zoroastrianism is dying out, because it has the disadvantageous trait of not allowing new converts. Mormonism is increasing rapidly because it has many advantageous traits which discourage adherents from leaving, encourage them to breed rapidly, creating new adherents, and requires all adherents to spend significant effort on spreading the faith. In the future, Mormonism will likely continue to calve new faiths, which will inherit many of these selectively advantageous traits, while Zoroastrianism, it seems likely, will sadly die out, and take its refusal to accept converts with it.
see (http://en.wikipedia.org/wiki/Meme#Memetic_accounts_of_religion)
- Instinct vs. biological behavioral predispositions.
There were several discussions yesterday that touched on instinct and evolved behavior, and treated the two as equivalent. They are not. Well, once again, it depends on the definitions. I hear behavioral ecologists, the biologists who study the evolution of behavior in relation to environment, argue about this one. Some define instinct as "evolved behaviors which require no learning or experience to perform correctly." Others use it as defined by http://en.wikipedia.org/...
Instinct is the inherent disposition of a living organism toward a particular behavior.
Taken this way, to mean any behavioral pattern influenced by inherited dispositions, everything we do can be said to be founded in instinct. "Human nature" is synonymous with "species specific behavioral patterns."
A great many things are blamed on human nature. Why we cheat. Why we fight. Why we enjoy dancing and solving puzzles. Why we respond in particular ways to certain colors or shapes or sound patterns. How we smile, how we cry.
I don't know what it means to say that these things are human nature unless we mean that there is something inborn in us that predisposes us to those behaviors. Our predispositions are the effect of our biology. Not all species have these predispositions. Why not? They didn't evolve to have those predispositions. Our evolutionary background has determined our neural infrastructure, our hormones, our ability to learn and react to our environment.
Right here it is important to note that question "nature or nurture?" is wrong. There is no genetic expression in the absence of an environment. There is no learning, growth or neurologically mediated response in the absence of genes. Everything we do is an interaction of the two.
- The fact that a behavior is evolved does not imply that it is acceptable.
Infanticide by step-fathers is found in many mammals. It is common in primates. It is common in humans (not to say all stepfathers want to kill their step kids, but the rate of infanticide by step fathers is much higher). Infanticide is an evolved behavior. This does not make it acceptable. There is good reason to think we have an evolutionary predisposition to murder, rape, theft, lying, hypocrisy, voting Republican, you name it. Morality is, in part, resisting your evolutionary background.
- Race is a social construct, not a biological fact.
There are minor biological differences between people from different parts of the world. There is a biological predisposition to classify people, and judge them based on those classifications. But there is more biological diversity within the humans of Africa than in the rest of the world combined. The lines we draw between races are arbitrary, the result of biases that make us pay more attention to some traits than others. Humans cannot be cleanly divided up into races.
7.Selection is always in the context of environment.
Darker skin is advantageous in areas where UV radiation is strong, and skin cancer is a serious risk. Light skin is advantageous in areas where sunlight is weak, and rickets is a serious risk. Large bull elephants can out compete smaller ones when the competition is in the form of fighting for access to females. Smaller bull elephants may have the advantage when food resources are scarce and widely spread, and the biggest males have trouble finding enough food. A big brain is useful when trying to outwit competitors, but dangerous in other ways. Which direction selection pushes is always context dependent.
- Long term predictions about how a particular species will evolve are almost always wrong.
I will not infrequently see in the press predictions about what humanity will look like 100,000 years from now, or other long term predictions. The people who make these predictions often call themselves evolutionary biologist. They are charlatans hungry for attention. Even if we did know how the environment would change in the future, they would still be wrong. They have no idea what they are talking about. Ignore them. Evolutionary biology is a powerful predictive tool, but it is not a crystal ball. Shun the frumious bandersnatch.
- The level at which selection operates.
Imagine an organism that does something for the good of the population, at its own expense. Better yet, imagine half the individuals in a population put effort into acting for the good of the population, and the other half just act on their own self interest. The ones who maximize their own self interest get the benefit of the help of the other half, at no cost. The helpful half is taken advantage of. They are at a disadvantage. They die more, reproduce less. Assuming these behaviors are heritable, the next generation has more unhelpful individuals. Repeat for a few generations, and the helpers are gone. The population is worse off, but evolution doesn't care. Evolution is not a conscious entity, and therefore cannot care.
Individuals can increase their own fitness by helping kin (who carry the same genes they do) or through reciprocity (I help you, you help me) and in some cases these things help the species as a whole. But there is no example I know of in which any species has evolved to do things because they are good for the species.
There was some discussion yesterday about whether selection happens at the level of individuals or genes. Without getting into too much detail, the answer is, both. Selection can act both on individual genes and on the bundles of interacting genes we call individuals.
- An objective observer would almost surely count humans as a third chimpanzee species.
Jared Diamond wrote a great book partly on this point.
http://en.wikipedia.org/...
To us, we seem vastly different from the chimps. By any objective measure, we are biologically so similar that it is pure hubris to claim we are completely distinct. We are far more biologically similar to them than many things that have been listed as being in the same species.
- Exaptation is one of the most important, and least understood phenomina in macroevolution.
Read this: http://en.wikipedia.org/...
Understand it. Bring it up the next time someone uses their failure to understand it to argue against evolution.
The key point is this:
One of the challenges to Darwin’s theory of evolution was explaining how complex structures could evolve gradually,[3] given that their incipient forms may have been inadequate to serve any function. As Mivart (a critic of Darwin) pointed out, 5 percent of a bird wing would not be functional. The incipient form of complex traits would not have survived long enough to evolve to a useful form.
As Darwin elaborated on in the last edition of The Origin of Species, many complex traits evolved from earlier traits that had served different functions. By trapping air, primitive feathers would have enabled birds to efficiently regulate their temperature, in part, by lifting up their feathers when too warm. Individual animals with more of this functionality would have left more offspring, resulting in the spread of this trait.
Eventually, feathers became sufficiently large that they enabled some individuals to glide. These individuals would leave more offspring, resulting in the spread of this trait because it served a second function, that of locomotion. Hence, the evolution of bird wings can be explained by a shifting in function from the regulation of temperature to flight.
While the chain of events that lead from feathers being non flight related to flight enabling is still open to controversy, almost everyone accepts that this process was an example of exaptation. Any time someone asks, "what good is half a (fill in the blank)?" explain exapation to them.
Tomorrow I will address more issues that came up from the comments, go in a bit more depth into mechanisms of evolution, and venture into why scientific language not only does, by must, differ from vernacular.