Summary

  • In this study the scientists compared 128 protein-coding genes of 55 animal species, representing all the large animal groups that we know.
  • The researchers found that most animal groups split much earlier than it was previously assumed.
  • According to the resеarchers the origin of most large groups of the animal kingdom stands in the Neoproterozoic, more than 700 million years ago.

When did the first multicellular organisms arise on earth – and thus the ancestors of all animals and plants? The answer on this question is still highly controversial, because of sufficient  fossil evidence. Numerous findings, however, prove that the ancestors of almost all animal species existed from the beginning of the Cambrian period, about 540 million years ago, from Crabs to Spiders to the ancestors of the deuterostomes (Marshall, 2006; Smith, 2013; Briggs, 2015). Also important body features such as the brain, the muscles or the heart were already present. These organisms of the Cambrian had so complex and varied blueprints that they could not have been the very first multi-cell-organisms. The origins of the animals must therefore go much further. In fact, researchers have discovered older multi-cell fossils, but they are partly controversial and extremely rare (Benton et al. 2015; Cunningham, et. al.  2017; Peterson et. al. 2007).

When did the "start shot" for the evolution of the multi-cell-organisms take place is therefore still unclear. In order to gain more insight, Martin Dohrmann and Gert Wörheide from the University of Munich used the molecular clock, to assess when the oldest animal strains were created.

For their study, they compared 128 protein-coding genes of 55 animal species, representing all the large animal groups that we know. The principle of the molecular clock is based on the fact that the progress of evolution genetic changes accumulates in the genetic material. If two stem lines divide from a common ancestor, their genetic make-up differs more the longer the separation occurred.

To the surprise of the researchers is that most animal groups split much earlier than it was previously assumed. They think that the origin of most large groups of the animal kingdom stands in the Neoproterozoic, more than 700 million years ago. The very first animals could have originated even a billion years ago. Their valuation  agrees with some paleontological and geochemical results, which are valid as evidence for animal life in the early Neoproterozoic.

Figure 1-© Dohrmann and Wörheide/ Scientific Reports, CC-by-sa 4.0 – Result of the molecular genetic dating: Most large groups in the animal kingdom goes back more than 700 million years.

 

The fascinating thing about it: The predecessors of today's animal groups existed already before the Ice-Age. The prehistoric animals must therefore have survived this cold season – despite drastic climate change and greatly altered living conditions in the primeval times.

If the results of the research confirms this raises, the question is what caused this early decomposition of the animals and how these animals survived the Ice-Age. In order to find the answers and to check their results, further analyzes with additional gene data and further optimized methods are now required, as they explain.

According to the researchers to make well-informed statements about the appearance and the  life of the early animals, we need a better understanding of the environmental conditions in the Neoproterozoic era as well as more fossils from this period, which can be clearly identified.

 

COPYRIGHT: This article is property of We Speak Science, a nonprofit institution co-founded by Dr. Detina Zalli (Harvard University) and Dr. Argita Zalli (Imperial College London). The article is written by Dardan Beqaj (M.Sc. Biology, University of Pristina).

 

REFERENCES:

https://www.nature.com/articles/s41598-017-03791-w

http://www.biotechniques.com/news/How-Evolutionary-Biologists-Calibrate-a-Molecular-Clock/biotechniques-366018.html#.WU1rMNR96mU

http://www.sciencedirect.com/science/article/pii/S0960982215009288

https://www.sciencedaily.com/releases/2017/06/170615084556.htm