'Lucy" exhibit: Science of humanity is still evolving

To begin with, when considering the story of human origins, it's perhaps important to recognize that scientists still don't agree on what it is exactly that seems to have made us so distinctive when compared with all the other animals running -- or swimming or flying, or just sitting -- around on Earth today.

Sure, we have big brains, but so do creatures like elephants and dolphins. Our close genetic cousin the chimpanzee uses tools and, arguably, a form of language to coordinate banana harvests, turf battles or other activities. The bottom line is we have yet to arrive at complete scientific consensus on what makes us human beings.

"Defining what is human from what is not human often just comes down to the personal proclivities of whomever you ask, but we do know the broad strokes," said Donald Johanson, director of Arizona State University's Institute of Human Origins and the famed paleoanthropologist who discovered Lucy. "One thing that's clear is that as we move further into the past, things get more apelike."

That much is certainly widely accepted as fact within the scientific community. The problems arise as you move forward, from ape to humans, and in resolving all the gaps, conflicting hypotheses and even apparent contradictions.

"That's what I love about the theory of evolution, that the theory itself is always changing," said Katherine Taylor, a forensic anthropologist with the King County Medical Examiner's Office who examines bones for clues about crimes and cause of death.

"As a forensic scientist, my examination and conclusions have to stand up in court," Taylor said. Much of the science she relies on is the same as that used in evolutionary science and based on distinctive, measurable characteristics of humankind. But she is not allowed the same freedom to speculate like the evolutionary theorists.

"All the new discoveries that keep adding to or changing the picture just makes it exciting," Taylor said.

"It's certainly more complex today than it was years ago," said Patricia Kramer, a paleoanthropologist at the University of Washington who studies human evolutionary adaptation. "It's not a simple dot-to-dot story anymore."

When Lucy was discovered more than 30 years ago, the main argument was over whether or not humankind evolved first by growing bigger brains or by standing upright on two legs, Kramer said. The leading anthropologists of the time, Louis and Mary Leakey, held that brains came first. Johanson eventually convinced most of his colleagues, if not the fiercely stubborn Leakeys, that Lucy proved bipedalism came before big brains.

But since then, Kramer said, we have learned many more things that make for a both a richer and more complicated story. The fairly recent discovery of fossils of a potentially new species of tiny humans -- dubbed the "Hobbits" -- who appear to have lived on an island in Indonesia some 15,000 years ago is just one monkey wrench. Because they had such tiny brains but lived contemporaneous with modern humans, she said, the simple version of our story has grown even more complicated.

"But that's the way science works," Kramer said.

It's never complete, never perfect and always at risk of disruption. "That's what makes it so much fun. This is an incredibly exciting time for paleoanthropology."