According to foreign media reports, the latest research shows that the earliest multicellular organisms may not have heads, legs or arms, but their fragments still remain in our bodies. According to a study by the University of California, Riverside, 555 million years ago, Ediacaran marine life had the same genes as animals today, including humans.
Mary Droser, a professor of geology at UCLA, said: "They don't have heads or skeletons. Many of them may look like three-dimensional non-slip mats on the seabed... These animals are so weird and so different that it's hard to classify them as modern creatures by observation alone, and we can't extract their DNA — we can't. ”
However, the well-preserved fossil record allows Drosor and the study's lead author, Scott Evans, ph.D., who recently graduated from UCLA, to link the animal's appearance and possible behavior to genetic analysis of current organisms. They published the findings in Proceedings of the Royal Society B.
In their analysis, the researchers believe that the four animals represent more than 40 known species of the Ediacaran period. The size of these creatures ranges from a few millimeters to nearly a meter.
Among them, Kimberella is a teardrop-shaped creature with one end wide and rounded and one end narrow. They could use "muscle feet" to move around like snails today. Other research subjects included flat, oval-shaped Dickinson jellyfish—with a series of raised stripes on their surfaces—and tripartites that have been fixed to the ocean floor all their lives.
In addition, the researchers also analyzed Ikaria, an animal recently discovered by a team that included Evans and Drosor. They are about the size and shape of a grain of rice, and they represent the earliest bilateral organisms. Evans said that although there is no record in the fossil record, Ikaria is likely to have a mouth, and they will crawl among organic matter "eating as they go."
All four animals are multicellular and have different cell types. Most of them are symmetrical on the left and right sides, and the nervous and muscular systems are not concentrated.
In addition, they appear to be able to repair damaged parts of the body through a process known as apoptosis. These genes are also key elements of the human immune system, which help to clear viral infections and precancerous cells.
These animals may have genetic parts responsible for the head and sensory organs. However, the complexity of the interactions between these genes that produce these traits has not been demonstrated.
"The fact that we can say that these genes work on something that's been extinct for 500 million years fascinates me," Evans said.
The research was supported by NASA's Space Biology Fund and the Peter Buck Postdoctoral Fellowship.
Next, the team plans to conduct studies on muscle development and function to further understand early animal evolution. "In some ways, our job is to put these animals on the tree of life and show that they are genetically connected to modern animals and us," Droser said.