Animal Life History: Were The Earliest Animals Microbial In Origin?

Scientists are currently attempting to further study the animal life history to trace the oldest forms of life in the kingdom Animalia. While there is no actual cast of a body to rely on, they have got fossils that are credible enough to show signs of animal life. The indications can be seen through scratches, footprints, burrows, or feeding marks. Through examination of animal fossils, experts found that there is a possibility for early animals to be microbial in origin.

According to Live Science, fossilized mats of stromatolites are the earliest evidence for existing life on Earth. Stromatolites are cyanobacteria that are around 3.7 billion years old.  Their DNA produces proteins and is protected by their cell walls. Due to being biologically complex, these cyanobacteria made scientists think that life might have possibly begun earlier.

Additionally, Phys.org reported that scientists believe they found fossils made by animals over a billion years ago. This further raised the speculation that animals might have existed this early. This is amidst the fact that animal remains appear to have existed 600 million years ago based on fossil records. According to the records, the first animals lived during the Ediacaran period when soft-bodied animals were extant.

Supposed animal trace fossils from the Ediacaran Period were examined by oceanographer Giulio Mariotti. With the help of his colleagues, he conducted an experiment and tried to create trails of grooves and pits that were very similar to the trace fossils. They created waves in the water, so that microbial aggregates would move across the sand and at the bottom of a tank of water. As a result, the aggregates produced various trails that are dependent to the aggregate size and wave conditions.

While the findings show possibility that the animal fossils have a microbial origin, questions were also raised about the trace fossils' reliability. The trails produced were very much similar to those that are called the Ediacaran trace fossils; and for this, it can be said that there is likewise a possibility that some of the "trace" fossils were just caused by the aggregates' movements and are not actual fossils.

Meanwhile, studying the earliest life on Earth is important to know the types of life that other planets might have. As of writing, more evidences are needed to show that the findings indeed show signs of early animal life. NASA Astrobiology Program, through its Exobiology & Evolutionary Biology element, funded the study.

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