Fossil hunters find evidence of 555m-year-old human relative

[muriel_volestrangler]

It might not show much of a family resemblance but fossil hunters say a newly discovered creature, that looks like a teardrop-shaped jellybean and is about half the size of a grain of rice, is an early relative of humans and a vast array of other animals.

The team discovered the fossils in rocks in the outback of South Australia that are thought to be at least 555m years old.

The researchers say the diminutive creatures are one of the earliest examples of a bilateral organism – animals with features including a front and a back, a plane of symmetry that results in a left and a right side, and often a gut that opens at each end. Humans, pigs, spiders and butterflies are all bilaterians, but creatures such as jellyfish are not.

Dr Scott Evans, of the Smithsonian National Museum of Natural History and a co-author of the research, said: “The major finding of the paper is that this is possibly the oldest bilaterian yet recognised in the fossil record. ​Because humans are bilaterians, we can say that this was a very early relative and possibly one of the first on the diverse bilaterian tree of life.”

https://www.theguardian.com/science/2020/mar/23/fossil-ikaria-wariootia-bilateral-organism-human-relative

Discovery of the oldest bilaterian from the Ediacaran of South Australia
The transition from simple, microscopic forms to the abundance of complex animal life that exists today is recorded within soft-bodied fossils of the Ediacara Biota (571 to 539 Ma). Perhaps most critically is the first appearance of bilaterians—animals with two openings and a through-gut—during this interval. Current understanding of the fossil record limits definitive evidence for Ediacaran bilaterians to trace fossils and enigmatic body fossils. Here, we describe the fossil Ikaria wariootia, one of the oldest bilaterians identified from South Australia. This organism is consistent with predictions based on modern animal phylogenetics that the last ancestor of all bilaterians was simple and small and represents a rare link between the Ediacaran and the subsequent record of animal life.

Abstract
Analysis of modern animals and Ediacaran trace fossils predicts that the oldest bilaterians were simple and small. Such organisms would be difficult to recognize in the fossil record, but should have been part of the Ediacara Biota, the earliest preserved macroscopic, complex animal communities. Here, we describe Ikaria wariootia gen. et sp. nov. from the Ediacara Member, South Australia, a small, simple organism with anterior/posterior differentiation. We find that the size and morphology of Ikaria match predictions for the progenitor of the trace fossil Helminthoidichnites—indicative of mobility and sediment displacement. In the Ediacara Member, Helminthoidichnites occurs stratigraphically below classic Ediacara body fossils. Together, these suggest that Ikaria represents one of the oldest total group bilaterians identified from South Australia, with little deviation from the characters predicted for their last common ancestor. Further, these trace fossils persist into the Phanerozoic, providing a critical link between Ediacaran and Cambrian animals.

https://www.pnas.org/content/early/2020/03/17/2001045117

[Wounded Bear]

1. Wow, that's a pretty misleading headline...

Finding an ancient mammal fossil is nice, but claiming it's an early "human" relative is a bit of a stretch, and not really very scientific. Not to mention, "bilaterans" are not strictly mammals, either.

[exboyfil]

2. Yes could be a cousin

All life on earth is a relative. The amazing thing is the predictive power of evolution. Even before this animal fossil was found, we would expect to find something like it from around this time. Not finding doesn't disprove evolution, but finding it helps to reinforce evolution.

Also another point to be made. Many creationists fall on the Cambrian "explosion" as evidence of a creation event. Virtually every precursor of that radiation has been found in fossils from before the Cambrian. These fossils are incredibly hard to find (small and soft bodied).

[muriel_volestrangler]

3. It's as much of a relative as you'd expect, 555 million years ago

'Mammal' would be a meaningless term that far back. The point is it's not one of the Ediacaran animals that may be no more related to us than jellyfish; they think this had a front and rear, muscles for forward movement, and maybe a gut too.

[Wounded Bear]

4. Well, they should have at least said "ancestor" instead of "relative"...

[muriel_volestrangler]

5. Ah, now that would be less scientific

When you find a fossil, it's very rare you can say "this is an ancestor". It's a species that fits with the wider characteristics you'd expect of an ancestor and its close relatives from that time. If you find someone in history with an unusual family name in a region you're looking for an ancestor in, it's likely to be a relative, but it could be a sibling of the direct ancestor - a many-times-great aunt/uncle.

They could have said "bilaterian", but that doesn't mean much to a lot of people, and needs the explanation of a paragraph.