What was the first creatures on earth

To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. The strange sea creatures known as Dickinsonia , shown here in fossil form, lived million years ago. The finding, published in Science on 20 September 1 , is based on a chemical analysis of fatty molecules preserved in the fossils.

It could alter the current story of how animals and other complex life arose. Researchers first discovered the pancake-shaped creatures — a group known as Dickinsonia — in the late s. Whereas most living things during that time ranged in size from microscopic to a few millimetres long, some Dickinsonia grew up to 1. Scientists have since debated whether Dickinsonia were primitive animals, giant single-celled organisms called protists, bacterial colonies or something else entirely.

A team led by Jochen Brocks, a palaeobiogeochemist at the Australian National University in Canberra, examined ring-like fat molecules called sterols that infiltrate the membrane surrounding a cell to keep it flexible and fluid. Plants, animals, fungi and bacteria all contain sterols, but the type of sterol that predominates in each group differs. Animals mainly make cholesterol, and the fungi that form colourful, crusty lichens found on boulders have only ergosterol. Fossils that contain these preserved biomarkers are rare, but strewn around the shores of the White Sea in northwestern Russia lie Ediacaran fossils — including Dickinsonia — embedded in a fossilized mat of algae, with their organic matter and fats perfectly preserved.

The latest findings also suggest that the transition between the Cambrian and the Precambrian, which includes the Ediacaran, was just another extinction event in which one animal community replaced another, Brocks says.

Analyses that have compared the DNA of living creatures today to trace back their evolutionary trees suggest that animals originated more than million years before the Cambrian — well before even Dickinsonia 2. This is really digging into that. Some within the scientific community are cautious about the findings.

We know there has to have been a time, an episode or an interval of hidden evolution in animals prior to million years ago. The question is — how far back did it go, and what was it like? Last update: 5 August Record number: Veuillez activer JavaScript. Por favor, active JavaScript.

Bitte aktivieren Sie JavaScript. Si prega di abilitare JavaScript. The mystery of the first animal denizen of the planet can only be inferred from fossils and by studying related animals today.

To get to the bottom of that, scientists analyzed massive volumes of genetic data to define the earliest splits at the base of the animal tree of life. The tree of life is a hierarchy of evolutionary relationships among species that shows which groups split off on their own evolutionary path first. The new study surprisingly found that the comb jelly was the first animal to diverge from the base of the tree, not the less complex sponge, which had previously been given the honor.

The results are detailed in the April 10 issue of the journal Nature , a journal that, like most respected journals, requires other scientists review a paper prior to publication.