Has the Origins of Human Life on Earth Been Discovered?

Asbo Zaprudder · Nov 10, 2021

Gingerbread Demon said:
Interesting so it's a hot debate then. Why?

The Problem With Defining Life | Science 2.0 (science20.com)
Can Science Define Life In Three Words? | Science 2.0 (science20.com)
Life Elsewhere in Solar System Could Be Different from Life as We Know It | National Academies

Brobdingnag said:
I beg to differ, life is usually quite easy to define. Viruses happen to be borderline. The question is at what point does "ordinary" or "regular" matter become "living" matter? It's the same thing about life and death of an individual. In 99 percent of the cases, there's no contest, even a layman can say this person is alive and that person is dead. However, there are always cases that are in the "maybe" zone and that require the opinion of experts who sometimes will not even agree with each other. It's the cases of "when do we pull the plug?"

Viruses are in that dividing zone. If we ever solve the case of the viruses, putting them unambiguously in "living" or "non-living" groups then there'll be some other beings that will find themselves on the border.

Please define what you mean by "life". I usually go by the NASA definition although I believe it might be somewhat restrictive in only considering chemistry.

Life is a self-sustaining chemical system capable of Darwinian evolution.

https://astrobiology.nasa.gov/research/life-detection/about/

By this definition, viruses are life although parasitic on other life. They are perhaps not life forms.

I think it's important to distinguish between life and life forms. An ecosystem is life but could it also be considered to be a life form?

One might also argue that the definition should include some statement about pattern replication. A definition for a life form might then be:

"A life form is a self-sustaining finite pattern capable of replication and Darwinian evolution through mutative variation of the pattern over successive generations."

I've dropped the mention of chemistry as I think that's too restrictive. For example, I believe simulated life forms also count. I'm also wondering about Darwinian evolution as perhaps somewhere out there, life is using a more Lamarckian mechanism. There is an epigenetic aspect to terrestrial life but it is not full blown Lamarckism.

In modern epigenetics, biologists observe that phenotypes depend on heritable changes to gene expression that do not involve changes to the DNA sequence. These changes can cross generations in plants, animals, and prokaryotes. This is not identical to traditional Lamarckism, as the changes do not last indefinitely and do not affect the germ line and hence the evolution of genes.

Biology:Alternatives to Darwinian evolution - HandWiki

Anyway, I don't think I'm necessarily correct. In the end, the concept of life is a purely human construct and it is all too easy to get tripped up by semantics. It would be easy if the universe stamped LIFE™ on everything living. Perhaps we should just take DNA (or RNA that can create DNA) as that trademark - at least for Earth.

rahullak · Nov 10, 2021

Would it be fair to say that in the spectrum of things in the world from non-life to life, viruses sit on the cusp and without viruses the mechanisms of replication could not have formed? In other words, do we have evidence that life as we know it could not have evolved without viruses coming into existence?

Asbo Zaprudder · Nov 10, 2021

rahullak said:
Would it be fair to say that in the spectrum of things in the world from non-life to life, viruses sit on the cusp and without viruses the mechanisms of replication could not have formed? In other words, do we have evidence that life as we know it could not have evolved without viruses coming into existence?

To replicate, viruses require complex cells that they can parasitise. We know that many cell genomes, including that of humans, contain large amounts of viral DNA. Viruses were not the first life forms on Earth but then neither were the current forms of eukaryotic, bacterial, or archaean cells. It's the chicken and the egg question taken farther back in time. For that question, the answer is neither really, and I suspect that might be the answer here also.

For interesting speculations on life's origins, read The Vital Question or Life Ascending: The Ten Great Inventions of Evolution by Nick Lane. Another viewpoint is to be found in Assembling Life: How Can Life Begin on Earth and Other Habitable Planets? by David Deamer.

For more general background about the evolution of life on Earth, there's A (Very) Short History of Life on Earth: 4.6 Billion Years in 12 Chapters by Henry Gee or Life on Earth (updated edition) by Sir David Attenborough.

rahullak · Nov 10, 2021

I'll probably read one or more of those books when I find the time. Thank you.

I am able to visualise, in the case of the virus, that it co-evolved with other chemical constructs. By this I mean, as evolution was occurring on the chemical soup, constructs that developed the parasitic replication mechanism co-evolved with other constructs that had begun to form replication mechanisms but resisted the parasitic replication. So in the process, both started to thrive because there were enough numbers of both that one did not overwhelm the other.

Very interesting.

Asbo Zaprudder · Nov 10, 2021

The main problem is preserving complexity in an environment that might not necessarily be conducive. Nick Lane discusses the problems involved very well. He and his team have been trying to simulate the processes that might have occurred in alkaline vents but I don't know if they've had much success. I suspect that fresh water pools where clays were present and fed by volcanic springs on the first islands might be the point of origin as proposed by David Deamer.

New book by biochemist David Deamer explores the origins of life

Since the discovery of deep-sea hydrothermal vents and the unusual forms of life inhabiting them, many researchers have focused on those environments as a likely site for the origin of life on Earth. But Deamer's research suggests there are significant problems with the notion that life began in salty seawater.

"We have proposed an alternative, which is that life began in freshwater hot springs associated with volcanic land masses that emerged from a global ocean around 4 billion years ago," Deamer said.

According to Deamer, the hot springs environment provides several important properties. Organic compounds delivered to Earth's surface by meteorites could accumulate in small pools and ponds. As water evaporates from those pools, a film of extremely concentrated compounds would form on the mineral surfaces.

"If the compounds can react, this is where it happens," Deamer said. "We have shown, both in the laboratory and in field experiments, that RNA-like polymers are synthesized from mononucleotides under these conditions. Furthermore, if lipids are present, the polymers become encapsulated to form microscopic protocells."

Multiple cycles of wetting and drying give the "protocells" an opportunity to become ever more complex, he said, and eventually they begin to evolve. Deamer and his colleagues have built an experimental system in his laboratory to simulate the wet-dry cycles of volcanic hot springs, and they have also conducted experiments at volcanic sites around the world, including Hawaii, Iceland, Kamchatka (in eastern Russia), New Zealand, and California's Mount Lassen.

"To my knowledge, no one else working on the origin of life has ventured out of the lab to see if their experiments actually work in conditions like those of the prebiotic Earth, but that's what we are doing," Deamer said.

The main components required for a primitive cell are an external membrane, genetic material, and a metabolism and we're not really sure in which order these developed. Some people think they arose simultaneously but that seems very unlikely to me. Nobody really has a good handle on the synthesis of the first nucleosides, which requires a nucleic acid cycle and probably postdates the origin of metabolic processes such as glycolysis but predates the citric acid or Krebs cycle.

Glycolysis - Wikipedia
Nucleic Acid Metabolism - Wikipedia
Citric acid cycle - Wikipedia

Another big problem is that early chemical pathways would have had to operate without suitable enzymes to speed things up. Protein enzymes couldn't exist until some primitive precursor of ribosomes had developed from RNA, which can also act as an enzyme. RNA is built from ribonucleotides such as adenosine 5'-monophosphate (AMP). The nucleoside adenosine is heavily involved in cell metabolism in the form of adenosine 5'-triphosphate (ATP), a closely related molecule. This seems to suggest that metabolism preceded RNA but some dispute this as they claim that polymerised nucleic acid sequences are required for evolution to work. Yet others claim that DNA must have preceded RNA as the 2-deoxyribose in DNA is more stable than the ribose in RNA. Making the first nucleotides, nucleosides, and their triphosphates without a helping hand from either RNA or protein enzymes is another part we really don't understand*. It's yet another chicken and egg problem.

How Life Began: New Research Suggests Simple Approach | Live Science

* Well I don't anyway.

publiusr · Nov 14, 2021

Prions/ Free Radicals aren’t life…Bacteria are. A virus is in between…although I look at the lunar lander looking phage as maybe nanotechnology

Asbo Zaprudder · Nov 14, 2021

All life on Earth (what we usually accept as life anyway) is powered by nanotechnology - the molecular machines inside our cells - albeit it's naturally evolved. Examples are ribosomes, ATP synthase, myosin, kinesin, dynein, and bacterial flagella.

Molecular motor - Wikipedia

ETA: Interesting YouTube video about evolution occurring for simulated "life" forms:

publiusr · Nov 15, 2021

I get get blobby, stringy shaped virons…that lunar lander thing is just visually…ugh..
You can heve cells breathe on their own
https://phys.org/news/2021-12-tissues-oxygen.html

Dryson · Nov 19, 2021

To replicate, viruses require complex cells that they can parasitise. We know that many cell genomes, including that of humans, contain large amounts of viral DNA. Viruses were not the first life forms on Earth but then neither were the current forms of eukaryotic, bacterial, or archaean cells. It's the chicken and the egg question taken farther back in time. For that question, the answer is neither really, and I suspect that might be the answer here also.

I was watching a Modern Marvels show on Copper and never realized how important the element was.

Without Copper in our bodies, we wouldn't live.
Copper is great for:

1. Killing viruses, which would have been important to early human as viruses would have surely eradicated humans without copper protecting us from the inside. Not all viruses though. But without Copper viruses would be able to kill a human in less than a week. Even the common cold would kill humans without Copper.

2. Copper is a great element to transfers a signal across. Once again without Copper atoms, most of the signals in the brain and in DNA and RNA would simply have a much shorter duration resulting in reduced mortality.

3. Copper is a also the best thermally conductive element know to humanity. Being able to transport energy throughout the body, which is regulated by the brain, allows the body to remain at a constant temperature that helps keep viruses and bacteria away along with creating super fluid reactions that help lube the body.

But when the human body incorporated copper into its DNA is a mystery. A mystery, if solved, would paint a better picture of when humans evolved on Earth or even possibly came to Earth after the evolution of the Earth had passed the liquid molten surface stage and hard rock and water, that was able to be swam in, was present on Earth.

Copper deficiencies might set us down the correct path of when humans began to incorporate copper into the development. Those with copper deficiencies could be ancestors to those early humans who had enough copper in their body to survive for maybe 50 years but not much longer than that.

Asbo Zaprudder · Nov 19, 2021

Copper plays an essential role in terrestrial biology but only as a trace element. Too much is toxic. The human body only contains between 50 and 120 milligrams of copper, which is used as a cofactor in many important enzymes. Its role is to act as an electron donor or acceptor in key redox (reduction-oxidation) reactions in essential metabolic processes such as mitochondrial respiration, melanin synthesis, collagen cross-linking, mopping up free radicals, and iron homeostasis.

Copper in health - Wikipedia
Copper Essential for Human Health (copperalliance.org.uk)

However, copper is not an element found in either DNA or RNA. If you want to "follow the money" to their origins, I suspect it would be best to consider environments where phosphates are available, the conditions under which purine and pyrimidine nitrogenous nucleobases can form, how ribose and deoxyribose sugars came to be attached to these molecules to form nucleosides, and how phosphate groups became attached to the sugars to form nucleoside triphosphates, nucleotides, and nucleic acids such as RNA and DNA.

Nucleoside triphosphate - DNA and RNA synthesis - Wikipedia

Santaman · Nov 19, 2021

What's next? Uranium?

Also copper is NOT the best conductor of heat, silver is better 400 vs 430W/m K.
Silver is a better electronical conductor at 15.9 n Ohm -m copper 16.8 n Ohm -m.
Do better research before throwing theories around just willy nilly, okay? I mean this took 2 minuyes of finding out.

Asbo Zaprudder · Nov 19, 2021

Santaman said:
Also copper is NOT the best conductor of heat, silver is better 400 vs 430W/m K.
Silver is a better electronical conductor at 15.9 n Ohm -m copper 16.8 n Ohm -m.

Actually, carbon in the form of graphite crystal is the best known thermal conductor with a maximum value of 4.18 kW/mK. For comparison, carbon in the form of diamond has a thermal conductivity of 2.2 kW/mK.

For engineering purposes such as computing, heat pipes are used to move heat efficiently by exploiting the phase transitions of a coolant within the pipe. Their effective thermal conductivity can range from 4 to 100 kW/mK. In practice, the range used for cooling electronics is from 1.5 to 50 kW/mK.

The most electrically conductive element at standard temperature and pressure (STP) is silver. Of course, superconductors are better but we don't know of any that work at STP.

I'm not entirely sure what happens with thermal conductivity in superconductors. I believe it falls rather than increases as phonon thermal conduction becomes dominant over electron thermal conduction below the critical point as free electrons are no longer available.

ETA: Excellent discussion (albeit very long) of what we know and don't know about the origin of the genetic code:

Santaman · Nov 19, 2021

Thought I'd stuck to metals on this one..

if you want it cheap and light you always can use aluminium for a heatsink.

Asbo Zaprudder · Nov 19, 2021

Fun fact for today: in astronomy, all elements other than hydrogen and helium are classed as metals.

Metals | COSMOS (swin.edu.au)

Dryson · Dec 2, 2021

Asbo Zaprudder said:
Copper plays an essential role in terrestrial biology but only as a trace element. Too much is toxic. The human body only contains between 50 and 120 milligrams of copper, which is used as a cofactor in many important enzymes. Its role is to act as an electron donor or acceptor in key redox (reduction-oxidation) reactions in essential metabolic processes such as mitochondrial respiration, melanin synthesis, collagen cross-linking, mopping up free radicals, and iron homeostasis.

Copper in health - Wikipedia
Copper Essential for Human Health (copperalliance.org.uk)

However, copper is not an element found in either DNA or RNA. If you want to "follow the money" to their origins, I suspect it would be best to consider environments where phosphates are available, the conditions under which purine and pyrimidine nitrogenous nucleobases can form, how ribose and deoxyribose sugars came to be attached to these molecules to form nucleosides, and how phosphate groups became attached to the sugars to form nucleoside triphosphates, nucleotides, and nucleic acids such as RNA and DNA.

Nucleoside triphosphate - DNA and RNA synthesis - Wikipedia

Copper is not an element found in either DNA or RNA

The results of this study indicate that the DNA double helix contains at least two kinds of binding sites for copper. One site is present once every four nucleotides, has high affinity, and shows a cooperative effect. The other is an intercalating site for copper that is present in every base pair.

In single-stranded DNA, we found an average copper binding site every three nucleotides with lower affinity than in dsDNA. The binding of copper to DNA shows an unexpected high specificity when studied in the presence of other metallic ions.

https://pubmed.ncbi.nlm.nih.gov/1949015/

Asbo Zaprudder · Dec 2, 2021

Yes, and? Copper ions can bind to single DNA strands and cause damage or impede decoding, mitosis, and meiosis. So what? So can Platinum as used in some cancer treatments. Copper is still not an element that is naturally found in DNA. Only C, H, O, N and P are - not S, not Fe, and seemingly not Cu.

Dryson · Dec 2, 2021

Copper is a trace element, important for the function of many cellular enzymes. Copper ions can adopt distinct redox states oxidized Cu(II) or reduced (I), allowing the metal to play a pivotal role in cell physiology as a catalytic cofactor in the redox chemistry of enzymes, mitochondrial respiration, iron absorption, free radical scavenging and elastin cross-linking.

With copper being an important trace element found in human DNA, where copper is in a pivotal role in cell physiology as a catalytic, determining the factors that allowed copper to bind with human DNA, cold, warmth, wet, dry, UV saturation, solar wind pressure and gravity of the Earth when copper would have easily have been able to bind to human DNA, would set up a time table.

A time table that future space telescopes could use to determine if such an environment exists in a solar system that would allow for life to benefit from copper.

The next important factor is to determine how much copper binds to human DNA and what type of environmental factors and when in the timeline of the evolution of the Earth the environmental factors existed that first bound the copper together that then binded with sites on human DNA.

Since humans do not have copper in our bodies naturally, but copper must be ingested, the timeline of humans gaining the ability to bind copper to DNA sites would be best determined by investigating the evolution of plants on Earth.
Copper rich plants that an early form of human life, not as we see ourselves in the mirror each morning, would have ingested where the proper amount of copper was present in the plant that then binded to the DNA sites.

Asbo Zaprudder · Dec 2, 2021

If you're going to quote verbatim from elsewhere, you should at least link to that site:

Copper is a trace element, important for the function of many cellular enzymes. Copper ions can adopt distinct redox states oxidized Cu(II) or reduced (I), allowing the metal to play a pivotal role in cell physiology as a catalytic cofactor in the redox chemistry of enzymes, mitochondrial respiration, iron absorption, free radical scavenging and elastin cross-linking. If present in excess, free copper ions can cause damage to cellular components and a delicate balance between the uptake and efflux of copper ions determines the amount of cellular copper.

Trace elements in human physiology and pathology. Copper | Request PDF (researchgate.net).

Copper ions damage single strand DNA (and presumably RNA) as the link in your previous post details but you do not - not only nucleic acids in humans by the way - there is nothing special about those. I doubt you even read the text at that link. You seem to have have drawn your own conclusions first, then searched on Google for copper and DNA, and, subsequently, just thrown in references to serious scientific work with the vague hope that some of them make sense in the context of your thesis.

Santaman · Dec 2, 2021

^^ You're using logic and reason again, he'll just skip to the next element.. :biggrin:

I'd go for Magnesium, really important! I mean it! We needs it the preciousssss..! :evil:

Asbo Zaprudder · Dec 2, 2021

The presence of phosphorus and absence of iron and sulfur in RNA, DNA, ATP, GTP etc. might be important clues as to the environment where these molecules originated - other heavy metal ions, not so much I think.

Iron–sulfur world hypothesis - Wikipedia

Has the Origins of Human Life on Earth Been Discovered?

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