Animal life may have existed 890 million years ago: Canadian scientist
A Canadian scientist has claimed to have found evidence of the oldest form of animal life, in the form of sponges, on Earth, dating back 890 million years ago or about 350 million years older than what is currently the case.
These findings were published by Elizabeth Turner, sedimentary geologist and professor with the Harquail School of Earth Sciences at the Laurentian University in Sudbury, Ontario. Her peer-reviewed paper was published by the journal Nature.
In the paper, she stated, “If the Little Dal objects are truly sponge body fossils, they are older than the next-youngest undisputed sponge body fossils (Cambrian) by approximately 350 million years.”
Little Dal refers to the area with the reefs containing the sponge fossils which were discovered in the northwest territories of Canada.
Cambrian refers to the period approximately 541 million years ago which is associated with an “explosion” of the first animals on the planet, as per fossil records. According to an article in Nature accompanying the study, these included arthropods, molluscs and worms.
In response to emailed queries from the Hindustan Times, Turner said, “If I am correct in my interpretation of the material, it establishes that animals were already present by 890 million years ago.”
That would make these “350 million years older than the next-youngest undisputed sponge fossil”.
Though this may seem a big difference, she said it was “actually not all that surprising. We already knew that animals must have had a lengthy evolutionary history prior to the appearance of mineralised animal body fossils (such as shells and exoskeletons) in rocks younger than 540 million years. Molecular clock estimates place the origin of sponges in the same time-frame as the age of the rocks I worked on, and so it is not surprising to find possible physical evidence of sponges at that time”.
She explained that sponges are the most basic animal in the animal tree of life, so it would not be surprising that the earliest animals may have been sponge-like.
Turner collected the samples as a student from the ancient reefs and has argued they display complex structures unlike cyanobacteria and algae. She said, “I initially discovered the material accidentally several decades ago while working on my unrelated PhD research.”
The idea “gestated” in her mind, but what finally allowed her to publish was that there “have been a number of recent papers on how sponges get preserved, and that’s the information I needed to support the interpretation of my own strikingly similar but much older material”.
According to an accompanying article in Nature, Turner examined her samples, slices of rock, under a microscope and saw “branching networks of crystalline tubes” which she “later realised” were structures resembling “the internal scaffolding of modern horny sponges, and line up with the expected decay and fossilisation patterns of spongin, a collagen protein that forms their scaffolding.”
The argument forwarded is that these crystalline tubes seen in the rocks could have formed when the collagen-like skeleton of the 890-million-year-old sponges decayed and fossilised.
Despite the adverse low-oxygen environment, the sponges could have survived on oxygen released by photosynthetic cyanobacteria and being nourished by the “organic ooze” these microorganisms generated.
As the Nature study appeared, Laurentian University tweeted, “We should note Dr Turner’s discovery would be the oldest form of animal life discovered on Earth.”
The Nature article also cited scientists questioning the findings and seeking further evidence before arriving at the conclusion these animals, the sponges, existed nearly nine million centuries back.
Asked about her confidence in the discovery, she replied the evidence is “very distinctive to sponges, and does not compare favourably to other possible interpretations such as microbial, algal, or fungal”. While she is “reasonably comfortable publishing” the findings, she added her “main intent” was to “present a new type of evidence and a logical interpretation of it, and then open it up to the scientific community for discussions”.