Was Human Life Dependent on Five "Hard Steps"?

I wish I knew! THIS PAPER suggests not, but first of all - What Are The Five Steps? They are the things which had to happen for human life to exist. And it is soon evident that much academic blood has been spilled over the compilation of the list. But here is one version of it.

1. Life (abiogenesis)
   
   
2. Oxygenic photosynthesis
   
   
3. Eukaryotic cells - fusion of a Bacteria with an Archaea
   
   
4. Animal multicellularity
   
   
5. Homo sapiens

The order of the steps is fixed. Steps 1, 3 and 4 are evolutionary steps, 2 and 5 are not. Various other steps have been proposed but five seems a good number. A definition of a hard step is:- Improbable, and essential for the evolution of humanity.

These hard steps are fairly evenly distributed over the life of the Earth.

The authors of this article suggest that these singularities are the result of the global-enviromental processes. They may have happened once but the happening was inevitable.

This is a very interesting article and you need to read it to get an appreciation of the knowledge used in it. But the conclusion seems to imply that human like beings should be fairly common in the universe. So far we have discovered only us. Are the authors wrong or is there something preventing intragalactic communication?

 Down to Earth Extra March 2025

The March 2025 edition of Down to Earth Extra has been published. You can download it HERE or you can read it below.

 Does the Inner Core Change Shape?

And if it does, how do we tell and does it matter? The Inner Core is solid, the Outer core is liquid. Both are thought to be largely iron. The Core is responsible for the Earth's magnetic field, without which life on Earth would not be possible. And it is studied by using earthquakes, specifically those in the South Sandwich Islands and recorded in Northern Canada, passing through the earth's core on their way.

There is no shortage of South Sandwich earthquakes and many are very similar. Over the years their signature in Northern Canada has shown differences. The differences have been attributed to the Inner Core rotating at different speeds and lately the differences have been thought to be because of changes to the cores shape.

The above is a very superficial reading of the research. If you want to know more there is the BBC ARTICLE which is based on this SCIENTIFIC PAPER. The diagram below might help to understand the research.

 Jurassic Coast Trust to Close

A correspondent alerted me to this. Details can be found on THIS BBC WEBPAGE. At least the Jurassic Coast is still open. But it is very sad.

 Down to Earth Extra February 2025

The February 2025 edition of Down to Earth Extra has been published. You can download it HERE or you can read it below.

 Fish Vomit Fossilised

A correspondent sent me THIS LINK, for which I thank him. It concerns the find by an amateur fossil hunter of what turned out to be fish vomit. It consist of all the indigestible bits of what some fish had eaten. You can see bits of crinoid.

It comes from Stevns Klint which has some renown as a place where the contact between the Cretaceous and Paleogene can be seen, with its iridium enriched layer.

The specimen comes from the Cretaceous and helps us envisage life beneath the waves at that time.