Texas Evolution Update

Scientists are celebrating in Texas today—or are they? The Texas state board of education on Friday tentatively approved new science standards, the basic blueprint that spells out what

students are expected to know in that subject. The overwhelming focus has been on how the document would treat evolution. The existing version of the standards, which have been around since

1998, call for students to learn about the “strengths and weaknesses” of various scientific theories. Scientists have long complained about that wording, basically arguing that certain

critics are only interested in examining what they believe are weaknesses in one theory in particular: evolution. Doing so is misleading, to say the least, most scientists say, because

evolution is one of the best-supported principles in all of science. So today, after many twists and turns, the board today tentatively approved standards that do not include the “strengths

and weaknesses” language, a move likely to hearten many scientists. The revised document instead says that students should use “critical thinking, scientific reasoning and problem solving to

make informed decisions within and outside the classroom,” and that they are expected to “analyze and evaluate scientific explanations using empirical evidence, logical reasoning, and

experimental and observational testing.” The board specifically rejected an amendment to re-insert the strengths-and-weakness language. But you can bet that a lot of biologists (not to

mention chemists, anthropologists, and others) will be less enthused about another action by the Texas board. Its members approved an amendment that asks students to “analyze and evaluate

the sufficiency or insufficiency of common ancestry to explain the sudden appearance, statis, and sequential nature of groups in the fossil record,” according to the Texas Education Agency.

A few advocacy groups following the debate in Texas have already put out statements calling this statement an attempt to undermine the teaching of evolution. Common ancestry is a key concept

in evolutionary biology, and one the public often misunderstands. I could try to explain it, but I’d rather quote from “Science, Evolution, and Creationism,” a very readable booklet

published by a pair of prestigious institutions, the National Academies and the Institute of Medicine, in 2007: _ “Each species that lives on Earth today is the product of an evolutionary

lineage — that is, it arose from a preexisting species, which itself arose from a preexisting species, and so on back through time. For any two species living today, their evolutionary

lineages can be traced back in time until the two lineages intersect. At that intersection is the species that was the most recent common ancestral species of the two modern species.

(Sometimes, this common ancestral species is referred to as the common ancestor, but this term refers to a group of organisms rather than to a single ancestor.) For example, the common

ancestor of humans and chimpanzees was a species estimated to have lived 6 to 7 million years ago, whereas the common ancestor of humans and the puffer fish was an ancient fish that lived in

the Earth’s oceans more than 400 million years ago. Thus, humans are not descended from chimpanzees or from any other ape living today but from a species that no longer exists. Nor are

humans descended from the species of fish that live today but, rather, from the species of fish that gave rise to the early tetrapods If the common ancestor of two species lived relatively

recently, those two species are likely to have more physical features and behaviors in common than two species with a more distant common ancestor. Humans are thus far more similar to chimps

than they are to fish. Nevertheless, all organisms share some common traits because they all share common ancestors at some point in the past. For example, based on accumulating fossil and

molecular evidence, the common ancestor of humans, cows, whales, and bats was likely a small mammal that lived about 100 million years ago. The descendants of that common ancestor have

undergone major changes, but their skeletons remain strikingly similar. A person writes, a cow walks, a whale swims, and a bat flies with structures built of bones that are different in

detail but similar in general structure and relation to each other.” _(p. 24) Whether the document approved by the Texas board appeals to you or offends you, know this: It’s not over yet.

The panel is scheduled to meet in March to vote on a final version of the science standards.