Missing a Link Between Past and Future.

At long last, fossil hunters have found the coveted "missing link." Again.

Even before naturalist Charles Darwin — born two centuries ago this year — published "On the Origin of the Species," the phrase "missing link" had entered the lexicon. It quickly became a kind of shorthand criticism of evolution, as in "they've yet to find the missing link" between humans and apes.

But that's getting a bit ahead of the story. Or, perhaps, behind it.

In any case, the latest missing link is a 47-million-year-old animal found in a German quarry. Researchers have dubbed her Ida. They believe she might tie early primates to the evolutionary branch that later developed into great apes and humans.

If they're correct, we come from unimpressive stock. Ida is about the size of a small monkey, with a long tail and splayed opposable thumbs — more reminiscent of a tree-dwelling lemur than a chest-pounding gorilla.

In the popular imagination, of course, the missing link is a half-human, half-ape with terrifying strength and modest cognitive abilities.

The quest for that particular missing link, and the fascination that fueled it, lies in the idea of capturing a flickering instant in time before we humans became, well, humans. Discoveries of ancestors like Homo erectus and Australopithecus africanus ended the search for that missing link, as Brian Palmer notes in Slate.

In a broader and more modern sense, though, there are as many missing links as there are branches in the tree of life. Scientists call them "transitional forms" or "transitional morphologies." But headline writers prefer a punchier phrases, so "missing link" has been used to describe new fossil discoveries at least 28 times in the last decade, Palmer calculates.

For example, Tiktaalik — a 375-million-year-old fossilized fish discovered in 2006 on an island in northern Canada — is a missing link between animals that lived exclusively in water and those that lived exclusively on land.

Archeopteryx, the so-called "feathered dinosaur" is another. Others represent intermediate forms from amphibians to reptiles and from reptiles to mammals.

In 2007, Newsweek magazine asked Americans their views on evolution. Just 48 percent said they believe it is both well accepted in the scientific community and well supported by the evidence.

The reality is that evolution is the foundation of modern biology. It is accepted overwhelmingly by scientists because the evidence is overwhelming.

The discovery of Ida is unlikely to change many minds. For one thing, she looks so little like modern humans. For another thing, people tend to substitute their own ideas about human life and its role in the cosmos for reasoned examination of the evidence for evolution.

Thus, fossil evidence becomes a kind of Rorschach test that turns education policy into a battleground.

Earlier this year, education officials in Texas narrowly beat back proposed changes in the state science curriculum that would have encouraged students to "critically examine" the theory of evolution — though not the theory of gravity or any other scientific theories.

Such skirmishes probably will continue. That's unfortunate, because knowing the past is crucial to understanding who we are today. The real question isn't where we came from; it's where we're going and how we get there.

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