Fred Heeren, Boston Globe

CHENGJIANG, China — The fish-like creature was hardly more than an inch long, but its discovery in the rocks of southern China was a big deal. The 530-million-year-old fossil, dubbed Haikouella, had the barest beginning of a spinal cord, making it the oldest animal ever found whose body shape resembled modern vertebrates.

In the Nature article announcing his latest findings, Jun-Yuan Chen and his colleagues reported dryly that the ancient fish “will add to the debate on the evolutionary transition from invertebrate to vertebrate.”

But the new fossils have become nothing less than a challenge to the theory of evolution in the hands of Chen, a professor at the Nanjing Institute of Paleontology and Geology. Chen argues that the emergence of such a sophisticated creature at so early a date shows that modern life forms burst on the scene suddenly, rather than through any gradual process. According to Chen, the conventional forces of evolution can’t account for the speed, the breadth, and one-time nature of “the Cambrian explosion,” a geologic moment more than 500 million years ago when virtually all the major animal groups first appear in the fossil record.

Rather than Charles Darwin’s familiar notion of “survival of the fittest,” Chen believes scientists should focus on something that better explains why life evolved beyond bacteria. “Bacteria are very successful,” Chen notes. In fact, complex life is less capable of making adaptations.

If all we have to depend upon is chance and competition, Chen says, then “complex, highly evolved life, like the human, has no reason to appear. So why should these chance mutations plan such complex types of animals?” Chen proposed that an underlying principle of “harmony” will someday explain what competition cannot.

The debate over Haikouella casts Western scientists in the unlikely role of defending themselves against charges of ideological blindness from scientists in communist China. Chinese officials argue that the theory of evolution is so politically charged in the West that researchers are reluctant to admit shortcomings for fear of giving comfort to those who believe in a biblical creation.

“Evolution is facing an extremely harsh challenge,” declared the Communist Party’s Guang Ming Daily last December in describing the fossils in southern China. “In the beginning, Darwinian evolution was a scientific theory …. In fact, evolution eventually changed into a religion.”

Taunts from the Communist Party wouldn’t carry much sting, however, if some Western scientists weren’t also concerned about weaknesses in so-called neo-Darwinism, the dominant view of evolution over the last 50 years.

“Neo-Darwinism is dead,” said Eric Davidson, a geneticist and textbook writer at the California Institute of Technology. He joined a recent gathering of 60 scientists from around the world near Chengjiang, where Chen had found his first fishlike impressions of Haikouella five years ago.

But most Westerners at Chen’s conference came to praise Darwin, not to bury him. The idea that neo-Darwinism is missing something fundamental about evolution is as scandalous to Americans as it is basic to the Chinese.

However, despite their misgivings about Chen’s “harmony” proposal — a mysterious mix of scientific caution, Chinese philosophy, and a decidedly non-Western lack of concern for Darwinian orthodoxy — Western scientists have no choice but to go to China to learn about the emergence of animal body plans, including that of human forerunners.

Virtually all of today’s living phyla — or major animal groups — make their first impressions in the geologic period known as the Cambrian. And Chengjiang, in the southern province of Yunnan, contains the oldest and best preserved Cambrian fossils in the world. Jun-Yuan Chen has co-authored half of all the papers on the Chengjiang fauna.

Chen’s discovery of the earliest chordate, named for the “notochord” that would eventually form the vertebrate backbone, is, for him, but one more piece in a puzzle that looks less and less like the conventional picture of evolution through natural selection.

For Western paleontologists, Haikouella looks like a breakthrough for understanding the origin of the human lineage.

“It proves that the direct ancestor of mankind already existed in the time of the Cambrian explosion,” said German paleontologist Michael Steiner.

“Sort of instinctively, I felt I should go and pay homage to this animal,” said another scientist at the conference, Nicholas Holland, an authority on primitive chordates at the Scripps Institution of Oceanography in San Diego. “It’s the earliest known chordate ancestor. This is going to be page one, two, three and four of vertebrate texts.”

Chen enjoys seeing his fossils get the attention. But to him, the big story is not that he has discovered our earliest traceable ancestor, but that the Cambrian explosion of new body plans is proving to be real, not an illusion produced by an incomplete fossil record.

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