Scientists from the University of Cambridge may have found fossil evidence of very early reproduction in complex organisms. It is the oldest form of reproduction we have ever found in a complex organism.
The organisms seen in the fossil belong to the genus Fractofuses. These are examples of rangomorphs, a large group of early organisms that resemble ferns. It is unlikely, however that they are plants because they inhabited ocean floors that are very dark where little sunlight could reach. They may be some of the first animals to evolve but this is unclear. They were bound to the seafloor and were very simple compared to the complex organisms seen today.
The fossil, found on the coast of Newfoundland, show several organisms of various sizes clustered together. The team believes the fossil shows three different generations of the organism. Various different sizes are seen in the fossil. The large individuals are thought to be fully grown while smaller ones are younger. The younger individuals surround the older ones.
What scientists believe they are observing in this fossil in one of the first examples of asexual reproduction in a complex, multicellular organism. Asexual reproduction involves creating progeny that are genetically identical to the parent. Asexual reproduction is the method used by single celled life during and before the time of the Fractofuses but this involved the simple dividing of a cell. Asexual reproduction is Fractofuses would have been much more complicated. They think the parent sends out ‘runners’, which lead to smaller individuals surrounding larger ones. This is similar to how many plants reproduce. Propagation was also probably used. A cluster would release propagules, which would start an entire new cluster. The propagules would have resulted in the parent in the centre. This strategy would have allowed Fractofuses to quickly spread out over wide areas allowing it be very successful.
The fact that Fractofuses can use two different methods of asexual reproduction shows they were very complex for their time. Especially when considering most of the other life around it was single celled.
The fossils are thought to be about 565 million years old. This dates back to just before the Cambrian period where a very large variety of complex life evolved. As more complex life evolved, these rangomorphs were probably outcompeted.
Fractofuses did not have any gut or mouth and couldn’t acquire energy by photosynthesis so it is unclear how it obtained energy. It is hypothesized that they could gather dissolved nutrients in the water through osmosis, similar to how sea sponges obtain their food.
Rangomorphs disappeared from Earth fairly quickly so before this study, it was difficult to determine how they reproduced. This study shows they used advanced methods of asexual reproduction.