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New research reveals that animals first emerged in China

The finding is based on 518 million-year-old rocks containing the oldest collection of fossils on record.

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Fish (Myllokunmingia). (Dr. Xiaoya Ma / SWNS)

By Mark Waghorn via SWNS

Animals emerged out of China, according to new research.

Today's species - including humans - can trace their roots back to Chengjiang in the mountainous Yunnan Province in the southwest of the country.

It is where the development of complex creatures began - an event known as the 'Cambrian Explosion'.

The finding is based on 518 million-year-old rocks containing the oldest collection of fossils on record.

They include 250 different lifeforms ranging from the first worms to primitive arthropods that led to shrimps, insects, spiders and scorpions.

Even the earliest vertebrates are there - the ancestors of modern fish, amphibians, reptiles, birds and mammals.

Senior author Dr. Xiaoya Ma, of Exeter University, said: "The Cambrian Explosion is now universally accepted as a genuine rapid evolutionary event.

Lobopodian worm (Luolishania). (Dr. Xiaoya Ma / SWNS)

"But the causal factors have been long debated - with hypotheses on environmental, genetic or ecological triggers."

At the time the area was a vast wetland feeding the mouth of a river - ideal for organisms to thrive.

Dr. Ma said: "The discovery of a deltaic environment shed new light on understanding the possible causal factors for the flourishing of these Cambrian bilaterian animal-dominated marine communities and their exceptional soft-tissue preservation.

"The unstable environmental stressors might also contribute to the adaptive radiation of these early animals."

Only true animals are 'bilaterian' - with both a front and back, two symmetrical sides and openings at either end connected by a gut.

An analysis of ancient sediment samples identified evidence of marine currents.

The area was a shallow, nutrient-rich delta affected by storm-floods - shedding fresh light on evolution.

Co-lead author Dr. Farid Saleh, of Yunnan University, said: "We can see from the association of numerous sedimentary flows the environment hosting the Chengjiang Biota was complex.

"It was certainly shallower than what has been previously suggested in the literature for similar animal communities."

The era was a key period when the diversity of life began to resemble that of today.

Most organisms were simple until then - composed of individual cells occasionally assembled into colonies.

Co-lead author Dr. Changshi Qi, also from Yunnan said: "Our research shows that the Chengjiang Biota mainly lived in a well-oxygenated shallow-water deltaic environment.

"Storm floods transported these organisms down to the adjacent deep oxygen-deficient settings, leading to the exceptional preservation we see today."

Arthropod (Naroia). (Dr. Xiaoya Ma / SWNS)

The study also confirms a long-held theory that a large spike in oxygen triggered the burst.

Co-author Professor Luis Buatois, of Saskatchewan University in Canada, said: "The Chengjiang Biota - as is the case of similar faunas described elsewhere - is preserved in fine-grained deposits.

"Our understanding of how these muddy sediments were deposited has changed dramatically during the last 15 years.

"Application of this recently acquired knowledge to the study of fossiliferous deposits of exceptional preservation will change dramatically our understanding of how and where these sediments accumulated."

The results in Nature Communications show early animals tolerated stressful conditions.

These included fluctuations in salt levels in water and high amounts of sediment deposition.

It contradicts previous suggestions that they colonized deeper and more stable marine environments.

Co-author Prof Gabriela Mangano, also from Saskatchewan has studied other well-known fossils of exceptional preservation in Canada, Morocco and Greenland.

She said: "It's hard to believe these animals were able to cope with such a stressful environmental setting."

The Cambrian Explosion is acknowledged as one of the most important intervals in the history of life on Earth.

Co-author Dr. Maximiliano Paz, also from Saskatchewan, said: "Access to sediment cores allowed us to see details in the rock which are commonly difficult to appreciate in the weathered outcrops of the Chengjiang area."

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