Decaying腐烂的，衰减的 corpses尸体 are usually the domain² of forensic³ scientists法医科学家, but palaeontologists have discovered that studying rotting fish sheds new light进一步提供消息 on our earliest ancestry⁴. The researchers, from the Department of Geology at the University of Leicester, devised a new method for extracting information from 500 million year old fossils -they studied the way fish decompose⁵分解，腐烂 to gain a clearer picture of how our ancient fish-like ancestors would have looked. Their results indicate that some of the earliest fossils from our part of the tree of life may have been more complex than has previously⁶ been thought.

Their findings have been published today, Sunday Jan 31, ahead of print in Advance Online Publication (AOP) of the science journal Nature on www.nature.com The work was funded by the Natural Environment Research Council全国环境研究委员会 (NERC).

Dr Rob Sansom, lead author of the paper explains: "Interpreting fossils is in some ways similar to forensic analysis法医鉴定法，法医分析 – we gather all the available clues to put together a scientific reconstruction⁷ of something that happened in the past. Unlike forensics, however, we are dealing⁸ with life from millions of years ago, and we are less interested in understanding the cause or the time of death. What we want to get at is what an animal was like before it died and, as with forensic analysis, knowing how the decomposition⁹ that took place after death altered the body provides important clues to its original anatomy¹⁰解剖."

This is something that palaeontologists sometimes overlook忽略, according to Sansom, "probably because spending hundreds of hours studying the stinking¹¹恶臭的，非常讨厌的 carcasses of rotting fish is not something that appeals to everyone." But the rewards are worth the discomfort¹².

Fish-like fossils from half a billion years ago are recognised as being part of our evolutionary¹³ history because they possess characteristic anatomical features, such as a tail, eyes and the precursor先驱，前导 of a backbone¹⁵脊柱. Sansom continues: "It seems contradictory矛盾的, but decomposition is an important part of the process by which animals become preserved and fossilized, so by knowing how these important anatomical features change as they rot, we are better able to correctly interpret the most ancient fossils representing the lowest branches of our part of the evolutionary tree."

"These fossils provide our only direct record of when and how our earliest vertebrate有脊柱的 ancestors evolved" adds Dr Mark Purnell, one of the leaders of the study. "Did they appear suddenly, in an evolutionary explosion of complexity¹⁷, or gradually over millions of years? What did they look like? – in what ways did they differ from their worm-like relatives and how did this set the stage for为……做好准备 later evolutionary events? Answers to these fundamental questions - the how, when and why of our own origins - remain elusive难懂的，易忘的 because reading the earliest vertebrate fossil record is difficult."

The scarcity缺乏，不足 of branches in this part of the evolutionary tree could reflect rapid, explosive evolution or the simple fact that, because they lacked bones or teeth, the earliest vertebrates脊椎动物 left few fossils.

This is the area in which Dr Sarah Gabbott, who with Purnell conceived构思，设想 the Leicester study, is an expert: "Only in the most exceptional circumstances do soft-tissues, such as eyes, muscles and guts²⁰, become fossilized, yet it is precisely²¹ such remains²² that we rely on for understanding our earliest evolutionary relatives: half-a-billion years ago it's pretty much all our ancestors had."

The results published today in Nature, show that some of the characteristic anatomical features解剖特点 of early vertebrate fossils have been badly affected²³ by decomposition, and in some cases may have rotted away completely. Knowing how decomposition affected the fossils means our reconstructions²⁴ of our earliest ancestors will be more scientifically accurate.