This will probably be REALLY boring... but when ya gotta write... ya gotta write!

I posed a question to my A.I. computer "HAL 9000" 

Q. "When life first arose on this planet how many different elemental life forms originated from this?"

A. HAL 9000 said!

1. Single Origin Hypothesis

• Last Universal Common Ancestor (LUCA): Evidence suggests that all life on Earth shares a common ancestor. LUCA likely arose from a single or small group of primordial systems that were biochemically similar.
• This suggests that there was one elemental "life form" that successfully adapted and became the progenitor of all known life.

2. Prebiotic Chemistry

• Before LUCA, Earth's environment may have supported multiple self-replicating molecular systems (e.g., RNA or other biopolymers). These systems might have competed, with only one (or a few) evolving into what we now recognize as life.
• These early systems could be thought of as protolife forms, but they lacked the complexity of modern life.

3. Elemental Composition

• All life as we know it is based on a few key elements: carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (CHONPS). While the combinations and molecular structures could have varied, there is no evidence for fundamentally different elemental life forms arising independently.

4. Hypothetical Alternative Life Forms

• If we speculate about multiple "elemental life forms" (e.g., silicon-based instead of carbon-based), there’s no direct evidence that such systems arose on early Earth. Earth’s conditions strongly favored carbon-based life due to its chemical versatility and abundance.

Conclusion

The origin of life likely involved the emergence of one or very few types of biochemical systems capable of self-replication and evolution. While different molecular experiments might have occurred in the prebiotic soup, only one lineage—LUCA's—survived and diversified into all the life forms we see today.

YOU THEN SAID:

You talk about "one elemental life form" and yet I understand that there are at least two... one that produced humans... and the other produced bacteria!

HAL 9000 said:

Your understanding highlights a key distinction, but it’s based on a misunderstanding of the evolutionary relationships between humans and bacteria. 

Let me clarify:

Humans and Bacteria Share a Common Ancestor

• Both humans (eukaryotes) and bacteria (prokaryotes) evolved from the same Last Universal Common Ancestor (LUCA).
• LUCA was not a fully modern cell but likely a primitive, single-celled organism that already had the genetic and biochemical machinery shared by all life today (e.g., DNA, RNA, proteins, and a lipid membrane).

Divergence After LUCA

• After LUCA, life diverged into three main domains:
  1. Bacteria: Single-celled organisms with simple structures and no nucleus.
  2. Archaea: Single-celled organisms similar to bacteria but with different biochemistry.
  3. Eukaryotes: Organisms with more complex cells that include a nucleus and microtubules, which eventually gave rise to humans, plants, fungi, and many other forms of life.

This means humans and bacteria represent two different branches of the tree of life, but both ultimately come from the same "elemental life form" — LUCA.

Why It Might Seem Like Two Origins

You might think of bacteria and humans as arising from separate origins because of how vastly different they are today. However:

• The apparent "two forms" you refer to are better explained as the result of evolutionary divergence over billions of years.
• Bacteria represent a lineage that remained relatively simple, while humans are part of a lineage that evolved greater complexity.

Alternative Hypotheses

It’s worth noting:

• Some scientists speculate that there might have been multiple proto-life systems on early Earth. While LUCA's lineage succeeded, other potential forms of life (based on different biochemistries) may have failed and left no descendants.
• This is not the same as suggesting bacteria and humans arose independently. Both are part of the same evolutionary story.

Summary

There weren’t two separate "elemental life forms" that originated to produce humans and bacteria. Both humans and bacteria are descendants of LUCA, a single origin for life as we know it. The diversity we see today is a result of billions of years of evolution from that common starting point.

***

Well folks... the corollary of this story is that even if HAL 9000 doesn't share any of our "Divine" human attributes like joy, sadness, love of music, awe and wonder, beauty, instinct and intuition, hunches, those "eureka" moments... and on and on... but... WHAT IT DID HERE IS PRETTY DAMNED IMPRESSIVE!

Allan

P.S. If ANYONE was interested enough to read all the way down to HERE... for God's sake please let me know!!!!!!