Evolution: origin of eukaryotes: 1.6 byo (Evolution)

by David Turell , Wednesday, June 07, 2023, 20:03 (325 days ago) @ David Turell

Based on finding protosteroides in rocks with fossils:

https://www.newscientist.com/article/2377272-1-6-billion-year-old-steroids-may-be-trace...

"The earliest life forms on Earth were simple single-celled organisms like bacteria that emerged more than 3 billion years ago. At some point – we don’t know exactly when – came more complex organisms called eukaryotes, whose cells have a nucleus. These eventually evolved into all the animals, plants, fungi and algae alive today.

"The oldest confirmed eukaryote fossils are red and green algae found in 1-billion-year-old rocks in Canada and China. Eukaryote fossils are confirmed by their shape and the detection of steroids – molecules that eukaryotes use to build cell membranes – co-located in the same rocks.

'Older fossils that look like they might be eukaryotes have been found in rocks dating back 1.6 billion years, but scientists haven’t been able to find the tell-tale steroid molecules that should be associated with them, which has created a conundrum.

"Now, evidence collected by Brocks and his colleagues suggests these older fossils are in fact eukaryotes, but a more primitive form that produced simpler steroid molecules known as “protosteroids”.

"When modern eukaryotes make steroids, including cholesterol, they follow a 12-step biochemical pathway. The molecules made in the first few steps are protosteroids. (my bold)

"Brocks and his colleagues found examples of these protosteroids in 1.6-billion-year-old rocks collected from the McArthur river mine near Borroloola in Australia’s Northern Territory, an area that once formed an ancient seabed. They did this by grinding up the rocks and then chemically analysing them.

"The researchers then studied a range of other rocks from around the world and also found abundant protosteroids in those aged between 1 billion and 1.6 billion years old.

"This finding suggests that the earliest eukaryotes emerged at least 1.6 billion years ago and made protosteroids. Around 1 billion years ago, eukaryotes evolved the ability to make modern steroids, which presumably conferred advantages that gave them the “upper hand” and allowed them to thrive while the earlier eukaryotes died out, says Brocks.

"These more sophisticated eukaryotes later evolved into algae, fungi, plants and animals that all produce modern steroids. The first animal eukaryotes, for example, emerged about 600 million years ago."

Comment: very suggestive, but much more has to be done to tie this up. Note my bold Twelve-step processes cannot happen from chance mutations.