Fossil discovery changes theory

Professor Li Chia-wei (above left) from the National Tsing Hua University in Taiwan and co-author of a report with Professor Chen Junyuan (right), from China, on the origin of vertebrate species, shown below, the fish-like Haikouella. PHOTO: LI CHIA-WEI

A team of scientists from Taiwan and China appear to have ushered in a new era of studying human evolution on earth, after revealing a recent discovery in China of the fossilized remains of animal life forms believed to be a common ancestor among vertebrates.

The fish-like Haikouella (®ü?fÂÎ) are believed to have been the first chordates (¯á¯Á°Êª«) with a clearly defined head and a large brain, according to a report in the latest edition edition of Nature, a leading international science journal.

The scientists said yesterday at a press conference in Taipei that their ten-member research team has discovered hundreds of Haikouella fossils preserved in excellent condition in southern China, and that the findings could well pave a new road in the story of the origin of later life forms, including humans.

"We believe that these 530 million-year-old fish-like fossils could rewrite the book on the origin of vertebrate evolution (¯á´Õ°Êª«), including the human species," said professor Li Chia-wei (§õ®aºû), from National Tsing Hua University in Taiwan, also the co-author of the report.

Nature, a British-based science journal, will publish a five-page report in its issue due out today, regarding this major discovery made by Li, and his coworkers, including professor Chen Junyuan (3¯§¡»·) and an assistant researcher Huang Di-ying (¶À-}¿o) from the Nanjing Institute of Paleontology and Geology in China.

Li said the discovery would also be included in the latest issue of the US version of the science periodical.

"We have discovered more than 300 fossil specimens in a small area, at Haiko, in Yunnan province. To memorialize the site where the extinct species was discovered, we named the ancestral vertebrate Haikouella," Li said.

Li said that although the fossils discovered are tiny -- between 2.5cm and 3.5cm in length -- details of their biological structure promise to be an inspiration to scientists.

"For the first time, we will be able, in exquisite detail, to trace vertebrates back to their invertebrate ancestors," Li said.

Showing slides of the fossils taken in Yunnan, Li pointed out that the Haikouella samples showed a clear line of evolution toward becoming vertebrates.

According to Li, the Haikouell is the first craniate chordate -- an animal form that featured a stiff rod (called a notochord) located above the gut and beneath a single, hollow dorsal nerve cord. They also had a distinct cranium.

"The discovery of the first craniate shows that the evolutionary history toward vertebrates had been on track long before the origins of the backbone," Li said.

As professor Chen pointed out in the report, due to the dearth of fossil evidence, human knowledge in the past had mistakenly assumed that the cephalization -- during which the head becomes the dominant body structure -- and full endoskeletonization -- when the body's superstructure is inside the body -- of vertebrates was a simultaneous development.

"Now, the Haikouella shows us that there is a prolonged history of cephalization before the origin of the backbone. The animals in the pre-backbone history that have a clear cranium, but no clear indication of endoskeletons or backbone, as "vertebrates" clearly transgress the manifest taxonomic principle of naming the organisms "vertebrates" based on the existence of a backbone," Chen wrote in the article.

Li, who holds a degree in biology from the University of California at San Diego, has been studying the mechanisms of biomineralization for years.

In 1998, Li and Chen jointly discovered fossils of embryos from the Precambrian era, millions of years before the evolutionary growth spurt known as the "Cambrian explosion." That discovery -- published simultaneously in separate reports in the most recent editions of Nature and Science -- looks set to rewrite the history of life on the planet. The discovery moved back the date of the earliest appearance of complex life forms on earth by 40 million to 50 million years.