Scientist Might Have Found Earliest Evidence of Animal Life on Earth

A Canadian scientist might have found the earliest evidence of animal life on Earth.

Geologist¹ Elizabeth Turner presented her findings in the science publication Nature in late July.

Turner made her discovery in the rocks of Canada's Northwest Territories. She has been doing research there since the 1980s. The area where she works has high mountains and can only be reached by helicopter. But an estimated 890 million years ago, the area was under the sea.

There, Turner said she found the remains² of sponges preserved as minerals in rock. The rock contains structures that look like modern sponges that live in the world's oceans.

Joachim Reitner is an expert on sponges at Germany's University of Göttingen. Reitner was not involved in the research. But he agreed the findings must be a kind of sponge.

Dating of rock levels suggests that the rocks containing the structures are about 890 million years old. That would make them about 350 million years older than the oldest sponge fossils found during earlier studies.

Paco Cardenas is an expert on sponges at Sweden's Uppsala University and was not involved in the research. He said the date of the sponge is the most shocking thing about it. Discovering sponge fossils from close to 900 million years ago will improve our understanding of early animal life, he said.

Many scientists believe the first animal groups included sponges or sponge-like creatures without muscles or nerves. But they had other qualities of simple animals, including cells for different purposes and sperm³ for reproduction.

However, there is very little scientific agreement about things that happened one billion years ago. So other researchers will continue to examine and debate Turner's findings.

"I think she's got a pretty strong case. I think this is very worthy⁴ of publishing. It puts the evidence out there for other people to consider," said David Bottjer. He is a paleobiologist at University of Southern California and was not involved in the research.

Scientists believe life on Earth appeared 3.7 billion years ago. The earliest animals appeared much later but exactly when is still debated.

The oldest undisputed fossil sponges date to around 540 million years ago, a time called the Cambrian period.

Some scientists using a method called the molecular⁵ clock say evidence suggests sponges appeared around a billion years ago. The molecular clock method dates changes in living things based on the idea that genetic⁶ change takes place at a regular rate over long periods of time.

But no supporting physical evidence for the first appearance of sponges had been found.

"This would be the first time that a sponge fossil has been found from before the Cambrian, and not only before, but way before — that's what's most exciting," said Cardenas. He added that the research seems to confirm the molecular clock estimates.

Little fossil evidence exists before the Cambrian period, when animals first developed hard bones, exoskeletons and shells. Those structures are more likely to be preserved.

The time period of 890 million years ago is important. If the organism is confirmed as a sponge, the discovery would prove that the first animals developed before oxygen reached a level scientists thought was needed for animal life. But recent research suggests that some sponges can survive with little oxygen.

"Everything on Earth has an ancestor," said Roger Summons. He is an MIT geobiologist who also was not involved in the research. He said it has always been predicted that the first proof of animal life would be small and mysterious.

Words in This Story

sponge –n. a kind of sea animal that lives in colonies and forms hard structures in the water

geologist –n. a scientists who studies the rocks to learn about the history of the Earth and its life

fossil –n. the remains of ancient plants or animals that have become preserved as minerals in rocks

muscle –n. body tissue that produces movement

paleobiologist –n. a scientist who studies ancient life

exciting –adj. causing a feeling of interest and energy

exoskeleton – n. a rigid covering on the outside of the body in some invertebrate animals

1 geologist   

n.地质学家

参考例句：

• The geologist found many uncovered fossils in the valley.在那山谷里，地质学家发现了许多裸露的化石。
• He was a geologist,rated by his cronies as the best in the business.他是一位地质学家，被他的老朋友们看做是这门行当中最好的一位。

2 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

3 sperm   

n.精子，精液

参考例句：

• Only one sperm fertilises an egg.只有一个精子使卵子受精。
• In human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中，一个精子使一个卵子受精。

4 worthy   

adj.(of)值得的，配得上的；有价值的

参考例句：

• I did not esteem him to be worthy of trust.我认为他不值得信赖。
• There occurred nothing that was worthy to be mentioned.没有值得一提的事发生。

5 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

6 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。