Was Life Brought to Earth by Asteroids?

A correspondent has brought THIS PROGRAMME to my attention - and it is pretty good! It explores the possibility that life arrived on Earth on board an asteroid. 

Maybe, but that just kicks the origin of life to someplace else. But it is still very interesting.

A source of other interesting programmes on the BBC can be found HERE.

 When was the First Animal?

A correspondent has sent me THIS LINK. The first fossils recognised as animals appeared in the Cambrian but were already complex beasties. Then animals earlier than the Cambrian were recognised even though they did not have hard parts - the Ediacaran fossils.

But how far back can we trace animals? There are ancient deposits which have all the signs of being a great place for animals to thrive but do not have animal fossils. But there are similar deposits of the same age which do! All very confusing. 

For several years the Weng'An biota (590 MA) was considered the base line - it should have fossils but didn't. But then a younger, similar, rock was found which should have fossils but also didn't. But there were undoubted fossils around at that time. So the absence of evidence should not be used as evidence of absence.

So deciding that the Weng'An was no longer the baseline the authors looked again at the molecular clock and decided that animal life could start earlier. So now animal life started, not at about 574MA, but between 800 to 720MA.

The link above is based on THIS ACADEMIC PAPER. This is much more detailed than the first link above and quickly becomes more complicated than I am comfortable with. So I asked Google Gemini to summarise it for me. This is given below.

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Summary of the Research

A study published in Science Advances led by researchers from the University of Oxford—alongside scientists from Berkeley, Yale, and ETH Zurich—suggests that the first animals on Earth may have evolved between 800 and 700 million years ago. This timeline pushes back the estimated origin of animal life by roughly 126 to 226 million years compared to traditional estimates based on physical fossils.

How Scientists Estimate Evolutionary Timelines

To pinpoint when ancient animal groups originated, evolutionary biologists use a tool called a "molecular clock." This method compares genetic differences in the DNA of living species to estimate how long ago their shared ancestors split.

However, genetic clocks require calibration using the fossil record:

• Minimum age limits: Set by the oldest undisputed animal fossil found in rock layers.
  
  
• Maximum age limits (ceilings): Set by rock formations known to preserve microscopic structures exceptionally well, but which completely lack any evidence of animal life. The assumption was that if animals had existed at that time, they would have been preserved.
  
  

The Breakthrough

For years, scientists used China’s Weng'an Biota (dated to ~590 million years ago) as a maximum age ceiling, assuming animal life could not have existed prior to it because no animal fossils were found there.

The researchers tested this assumption by comparing the Weng'an deposits to a rock formation in Mongolia called the Kheseen Biota (~550 to 526 million years old). The Kheseen rock preserved microscopic fossils under the exact same fine environmental conditions as Weng'an, but it contained no definitive animal fossils either—even though animals were unquestionably alive on Earth during that period.

Key Findings & Implications

• Absence of Evidence isn't Evidence of Absence: Because animals were absent in Kheseen despite existing at the time, the lack of animal fossils at Weng'an no longer serves as proof that animals hadn't evolved yet.
  
  
• Removing the Evolutionary "Ceiling": By dismantling the Weng'an maximum age restriction, calibrated molecular clocks allow animal origins to be placed much earlier, between 700 and 800 million years ago.
  
  
• Understanding Early Animals: Early animals were likely tiny, soft-bodied organisms that easily escaped preservation, explaining the gap between early genetic origins and later, larger physical fossils.
  
  
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 Clinopyroxenes - a Clue to Predicting Eruptions?

A correspondent has sent me THIS LINK concerning a paper about clinopyroxenes in rocks erupted in La Palma in the Canary Islands. The authors have examined, in excruciating detail clinopyroxenes erupted in three different eruptions. The research is also covered in "The Conversation" - see HERE.

These articles are all based on THIS PAPER in Nature. The authors have examined the crystals and have deduced an eruptive history of them by analysing the "growth rings" around the original core and from this deduce the following:- (this is an excerpt from a Google Gemini summary)

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Stagnant "Mush" Zones in the Upper Mantle: Deep beneath the island, around 18 to 25 kilometers (11–15 miles) down in the Earth’s upper mantle, magma sits in a cool (~1,000 to 1,025 °C), highly crystallized state known as a crystal "mush" (a sponge-like mix of mineral crystals and trapped liquid).

Recharge as an Unlocking Mechanism: At least one week prior to an eruption, fresh, hotter (~1,100 to 1,150 °C) magma surges up from deeper in the mantle. This hot recharge injects energy into the cool, sticky crystal mush, melting parts of it, unlocking the dense structure, and forcing the slushy mixture upward toward the surface.

Brief Stalling and Eruption: As the remobilized magma ascends, it may briefly pause in shallower crustal reservoirs (5–10 km depth) before erupting.

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The first thing which strikes me is the number of analyses - such a thing would have been impossible only a few years ago and unimaginable when I was a student. I also like them calling 1,000⁰ to 1,025⁰C cool!

They suggest that what they have found in the Canaries is applicable to other volcanic island and that the recharge - the second phase above - has a seismological signature which may be used to predict an eruption. 

 Super Volcano in "The Wash"!

This is the wrong part of the country for a West Country geological blog but I should have picked up on this earlier! In summary the BGS has found a late Ordovician (454.4 million years ago) super volcano under The Wash. The BGS has announced their findings in THIS NEWS release.

Once again zircons are the informant. The BGS drilled, found volcanic rocks containing zircons. These were dated and found to be the same age as those in ash deposits in Scandinavia. The ash deposits had been a mystery because the source was unknown. But now it has been found - under The Wash!

If you can stand it there is an intensely irritating YouTube video which tells you all about. It is irritating but it is actually accurate. Enjoy!!!

Down to Earth Extra October 2026

The October 2026 edition of Down to Earth Extra has been published, You can download it HERE or you can read it below.