English naturalist Charles Darwin published the & # 39; Origin of Species & # 39; more than 150 years ago
Darwinian evolution is a prominent scientific theory that describes how life forms develop through a process known as natural selection.
However, the latest research suggests that some of the widely accepted ideas about how animal species evolved on Earth need to be revised.
The latest findings suggest that the animal kingdom we occupy is much older than previously thought and diversified well before previous estimates, which located the arrival of most animal species during the Cambrian explosion 541 million years ago .
Writing for The Conversation, Dr. Jennifer Hoyal Cuthill, visiting researcher in paleobiology at the University of Cambridge, explains why ancient fossils are being reexamined and what research could mean for the timeline of life on Earth.
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English naturalist Charles Darwin published The Origin of Species more than 150 years ago. Darwinian evolution is a powerful scientific theory that describes how life forms develop through natural selection
When did the animals originate?
In an investigation published in the Paleontology journal, we show that this question is answered by fossils from the Cambrian period of a sea-fronted creature called Stromatoveris psygmoglena.
The Period of Ediacara lasted from 635 to 542 million years ago.
This era is key to understanding the origins of animals because it happened just before the "Cambrian explosion". of 541 million years ago, when many of the groups of animals that lived today first appeared in the fossil record.
However, when large fossils of the Ediacara period were identified for the first time during the 20th century, unique forms of fronds were included, which did not resemble any living animal.
This provoked one of the biggest debates still being fought in evolution. What exactly were these enigmatic fossils, often called the Ediacara biota?
Linkage of Ediacaran and Cambrian fossils
By comparing members of the Ediacaran biota with a number of other groups in a computerized analysis of evolutionary relationships, we find that Stromatoveris psygmoglena provides a crucial link between the previous period and the animals that appeared in surprising numbers and diversity during the Cambrian period. .
The fossils of Stromatoveris psygmoglena are found in only one place in the world: Chengjiang County, China. This region is known for exceptionally well preserved Cambrian fossils from 518 million years ago.
While the fossil record most often retains only shells or hard bones, some special sites such as Chengjiang preserve the remains of soft-bodied animals, such as Stromatoveris psygmoglena.
Originally described in 2006 from eight known specimens, we examined more than 200 new fossils from the organism that have since been discovered by researchers from the University of the Northwest, China, and dated in the Cambrian period.
The way in which the fossils of the Ediacarian Period were preserved has been another of their mysteries. These fossils often show signs of flexion, torsion and tearing, suggesting that they retain soft-bodied organisms with no hard parts.
However, there is rarely any soft tissue left.
Instead, they left molds in the surrounding sediment, a bit like a footprint on the beach.
When large fossils of the Ediacaran Period were identified for the first time during the 20th century, unique forms of fronds were included, which did not resemble any living animal. In the photo, an Ediacara fossil from the National Museum of Earth Sciences, Namibia
On the contrary, the recently examined Cambrian fossils of Stromatoveris psygmoglena retain the carbon-based tissue, which allows us to see the detailed and internal anatomy of the body itself.
During a research fellowship at the Tokyo Institute of Technology and the University of Cambridge, the fossils of the new Cambrian period of Stromatoveris psygmoglena were compared to the earlier Ediacaran fossils in a computer analysis of anatomy and evolutionary relationships.
This was also the first analysis to test the relationships between the Ediacara biota and a variety of other organisms, encompassing unicellular creatures called protozoa, algae, fungi and nine types of animals, including Stromatoveris psygmoglena.
This analysis used more than 80 photographs of individual fossil specimens to compare the anatomical characteristics of these groups.
The analysis showed that Stromatoveris psygmoglena and seven key members of the Ediacara biota share very similar anatomies, including multiple branched fronds that radiate outward like seaweed, joining them all together in a new group of primitive animals called Petalonamae.
The name means & # 39; Petals of Nama & # 39; and was chosen to honor the biologist Hans Pflug and his work on the Ediacara biota in Namibia, a reference to the petal-like fronds that, Pflug noted, distinguish these unusual animals.
Rethinking the evolution of animals
Joining these members of the Ediacara biota and Stromatoveris psygmoglena in a single group of animals has important implications for the origins of the animals. In light of this new evidence, some older ideas about early animal evolution may need to be revised.
The image shows a Cambrian fossil of Stromatoveris from the Northwestern University of China. The 'Cambrian Explosion & # 39; of 541 million years is when many of the groups of animals that live today appear for the first time in the fossil record
WHAT WAS THE EXPLOSION CAMBRIANA & # 39 ;?
Scientists have long speculated that a large peak of oxygen during the 'Cambrian Explosion & # 39; It was key to the development of many animal species.
The Cambrian Explosion, about 541 million years ago, was a period in which a great variety of animals broke into the evolutionary scene.
Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally arranged in colonies.
During the next 70 or 80 million years, the rate of evolution accelerated and the diversity of life began to resemble that of today.
It ended with the Cambrian-Ordovician extinction event, approximately 488 million years ago.
A recent study linked the historical increase in oxygen responsible for the formation of animal life on Earth with fossil fuels. In the image: this black slate, formed 450 million years ago, contains fossils of trilobites and organic material that helped these in oxygen
Because members of the Ediacara biota can now be classified as animals, we can date the origin of the animal kingdom at least until the time these fossils appeared.
The oldest members of these groups are known as & # 39; rangeomorphs & # 39; and appear in the fossil record about 571 million years ago, at the end of the Ediacara period.
This means that the animal species diversified long before the Cambrian explosion.
It may also mean that the search for animal origins must now focus on the previous time, on the first geological periods of Ediacara and even on the oldest ones.
Based on this, the animals may have originated much earlier than the traditional reading of the fossil record had suggested.
This study also has key implications for ecology and the eventual extinction of the petalonamides.
Many Ediacara species have not been found in later rocks leading some researchers to think that they were a "failed experiment" in evolution, disappearing at the beginning of the Cambrian.
In fact, this was my own opinion until I saw the remarkable new fossils of Stromatoveris psygmoglena.
The & # 39; Rangeomorphs & # 39; appear in the fossil record about 571 million years ago, at the end of the Ediacara Period. In the photo you can see the rangeomorph fossil, the oldest of the Ediacara biota
HOW HAS THE FORM OF OUR BRAINS BEEN EVOLVED WITH TIME?
New research suggests key evolutionary changes in the shape of our brain occurred 100,000 to 35,000 years ago. Stock image
Researchers at the Max Planck Institute for Evolutionary Anthropology in Germany discovered that the key evolutionary changes in the shape of our brain occurred approximately between 100,000 and 35,000 years ago.
The brain of Homo sapiens took a globe shape that is rounder and less protruding
On the contrary, the brains of our Neanderthal ancestors had a more elongated shape
The evolution of the shape of our brain coincided with important developments in behavior, when Homo sapiens began to:
- Build tools
- Develop a working memory and long-term
- Be aware of yourself
- Use language
- Activity plan
- Understand the numbers
- Pay attention to your surroundings
- Develop emotions
The brain began to look more like a globe as a result of the bulge in the parietal area and the cerebellum
The inclusion of this Cambrian animal among the petalonamides changes the image of the Ediacara biota.
Stromatoveris psygmoglena shows that the petalonamides were alive and were more than 20 million years old in the Cambrian period and did not become extinct from the beginning, as had been thought.
Even more intriguing, more than 200 fossils of Stromatoveris psygmoglena have been found, although they lacked hard parts that are generally more easily conserved.
This indicates that this species was an important member of its shallow marine ecosystem rather than a rare or marginal survivor.
This could mean that the petalonamides adapted more successfully to the changes of the Cambrian period than had been thought, or that the Ediacara period and its animals were less strange and more advanced than previously believed.
However, we can be sure that the animal kingdom we occupy is much older than we ever thought.
Dr. Jennifer Hoyal Cuthill is a visiting researcher in paleobiology at the University of Cambridge.
This article was originally published in The Conversation.