Thread: Can We determine extra terrestrial Biology using our own Biology

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Ok so I know that currently NASA have began work in this field. And that there have been specimens on earth(inconclusive ones though) but i just want to know. Could we possibly determine an aliens biology using our own. Would they have roughly followed the same laws of evolution as us(assuming the planet is a twin earth) or would they follow a completely different path such as cloud like figures that have electricity surging within them and this gives them consciousness?
Your opinions

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I am aware I was quite vauge there but I really want to learn off the replies so please reply with your thoughts

That off Earth life must exist.. Yes. Whats it like, and what might we ever find.. We have NO idea.
That we have as yet not a single case study.. not one.. expect different.
~ All else is open for your imagination to run riot.. speculate until sleep overwhelms your mind..

There are many planets that are millions of light years ahead of us so what those aliens would be like wouldn't be like us.

Would it be more reasonable to expect a watery environment as being more universally life friendly than the surface of planets? Could some of Earth's aquatic life here exist in the waters of other planets if placed there?

There must be extra terrestrial life. Theoretically it is a certainty. I am basing this off a scale that I would call almost an intelligence scale. So we have , Plankton/ then further along beavers, then at the top here Humans so there must be something more a more intelligent species

A big problem here is a shortage of examples. If one has only one example of something, it can be hard to tell whether it is necessary or else it is a historical accident. Small-number statistics can be difficult to do. Furthermore, in the evolution of life, there's the problem of whether something evolving only once means that it is difficult to evolve or else that it keeps competition from evolving by pre-empting it in some way.

So let's look at major events in the evolution of life on Earth.

All present-day organisms have one origin. Not only one origin, but a Last Universal Common Ancestor that had had a lot of evolution behind it. Judging from what present-day prokaryotes have, the LUCA had or likely had:

• DNA genome. DNA is a modification of RNA.
• RNA in various functions, likely a vestige of a RNA world.
• Proteins assembled in ribosomes from messenger-RNA templates and transfer-RNA amino-acid selection.
• Almost the same translation table for 3-nucleotide codons to amino acids.
• Electron-transfer energy metabolism: niacin, flavins, quinones, cytochromes, etc.
• Chemiosmotic energy metabolism: pumping hydrogen ions out of the cell membrane, and ATP-synthase complexes using their return to assemble ATP molecules
• ATP (the RNA nucleotide with extra phosphates) as an energy intermediate
• Biosynthesis metabolic pathways: many of them are the same across the Earth's biota

Some of the building blocks can be made prebiotically without much trouble, like the smaller protein-forming amino acids, some nucleobases, porphyrins, etc. But others are much more difficult, like ribose (in RNA). In fact, a major problem with the RNA-world hypothesis is the origin of the RNA.

The LUCA likely had poorly-developed DNA replication, since DNA-replication systems in the two kingdoms of prokaryotes, Bacteria and Archaea, have a *lot* of differences.

How did LUCA make a living? Chemiosmosis in the origin of life - 188.pdf

Despite thermodynamic, bioenergetic and phylogenetic failings, the 81-year-old concept of primordial soup remains central to mainstream thinking on the origin of life. But soup is homogeneous in pH and redox potential, and so has no capacity for energy coupling by chemiosmosis. Thermodynamic constraints make chemiosmosis strictly necessary for carbon and energy metabolism in all free-living chemotrophs, and presumably the first free-living cells too. Proton gradients form naturally at alkaline hydrothermal vents and are viewed as central to the origin of life. Here we consider how the earliest cells might have harnessed a geochemically created proton-motive force and then learned to make their own, a transition that was necessary for their escape from the vents. Synthesis of ATP by chemiosmosis today involves generation of an ion gradient by means of vectorial electron transfer from a donor to an acceptor. We argue that the first donor was hydrogen and the first acceptor CO2.

The authors also argue that fermentation is a later development, one that evolved several times. It is a rather complicated process, much more complicated than redox reactions, what happens in electron-transfer energy metabolism.

The organisms that successfully left the primordial soup/pizza/whatever were likely lithotrophic autotrophs, organisms that get their energy from inorganic-compound chemical reactions and make all their biological molecules. There are plenty of present-day ones, like methanogens.

However, lithotrophy depends on the presence of chemical disequilibrium, and that may be weak when away from volcanic gases, when away from places like hot springs and hydrothermal vents. An alternative is phototrophy or photosynthesis, getting energy from sight. It evolved two times.

Rhodopsin photosynthesis evolved in halophilic Archaea, and it involves a bacteriorhodopsin molecule absorbing a photon and changing its shape, pushing a hydrogen ion out of the cell membrane. It's plugged into chemiosmotic energy metabolism; the hydrogen ions are made to make ATP when they return.

Chlorophyll photosynthesis evolved in some early organism in Bacteria. Its early evolution is obscure, and it may have involved a lot of lateral gene transfer. It works by chlorophyll-containing antenna complexes energizing electrons with captured photons, much like photovoltaic cells. The electrons are then fed into the electron-transfer system where they can also be used for biosynthesis. Chlorophyll photosynthesis makes it possible to extract electrons from substrates that it takes a lot of energy to extract electrons from, like water, thus enabling its users to live in chemically neutral or oxidizing environments. This enabled its users to spread over most of the surface of our planet, including the illuminated parts of bodies of water.

So it evolved twice, with only one instance being useful for colonizing most of a planet's surface.

Multicellularity evolved several times, but a breakdown into types of multicellularity is revealing.

• Animallike: only once.
• Plantlike or algalike: several times. Prokaryotes: cyanobacteria (blue-green algae)
• Funguslike: several times. Prokaryotes: actinobacteria (actinomycetes)
• Slime-mold-like: several times. Prokaryotes: myxobacteria

This suggests that some other planet may have lots of multicellular organisms, but no multicellular animals. Lots of plants and fungi and slime molds, but the only animallike organisms are one-celled.

The animal kingdom being monophyletic, as they say in the phylogeny business, is well-established from molecular phylogenies. Animals' closest relatives are the choanoflagellates or collar flagellates. If some obscure worm was descended from ciliates or apicomplexans or rhizarians or euglenids or whatever, it would be rather obvious in gene comparisons. Even more to the point, patterning mechanisms like Hox genes are well-conserved over much of the animal kingdom.

Originally Posted by lpetrich

Multicellularity evolved several times, but a breakdown into types of multicellularity is revealing.

• Animallike: only once.
• Plantlike or algalike: several times. Prokaryotes: cyanobacteria (blue-green algae)
• Funguslike: several times. Prokaryotes: actinobacteria (actinomycetes)
• Slime-mold-like: several times. Prokaryotes: myxobacteria

This suggests that some other planet may have lots of multicellular organisms, but no multicellular animals. Lots of plants and fungi and slime molds, but the only animallike organisms are one-celled.

The animal kingdom being monophyletic, as they say in the phylogeny business, is well-established from molecular phylogenies. Animals' closest relatives are the choanoflagellates or collar flagellates. If some obscure worm was descended from ciliates or apicomplexans or rhizarians or euglenids or whatever, it would be rather obvious in gene comparisons. Even more to the point, patterning mechanisms like Hox genes are well-conserved over much of the animal kingdom.

~~ Much of what this contributor has offered is science based and impossible to argue with.. ( as the science decree permits.)
Only to add a point obvious and already made; That it happened here does NOT suggest it would or could be found as the same any place else.. I expect that the Universe is teaming with life.. Yet none of it might be as we have here.. As long as we have a case study of one. Our hands are tied to what we know, and it's not much is it ?
" Can we determine..//.." and the answer is No. We might yet find that RNA and DNA are the poor relative of whatever it is we find, or finds us.

The answer is that we can not use our idea of life to determine what might exist on other planets.
We don't even know enough about life as we know it to determine what it is like here, as we know it.

Discovery of "Arsenic-bug" Expands Definition of Life - NASA Science

"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new -- building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team's lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"

Life as We Didn't Know It - NASA Science

Before 1977, scientists believed that all forms of life ultimately depended on the Sun for energy. For all ecosystems then known to exist, plants or photosynthetic microbes constituted the base of the food chain.
In contrast, these vent ecosystems depend on microbes that tap into the chemical energy in the geyser water that billows out from the sea floor -- energy that originates within the Earth itself.

Except that the "arsenic bug" seems to be an unusually arsenic-tolerant organism, but one that nevertheless uses phosphorus in its genetic material: BBC News - Studies refute arsenic bug claim

It is the only model we know of so we can start from were we are, but until we find a sample of extra terrestrial life we are very limited. You can't deduce much form a sample of one.

I like to think of the evolution of a long river starting from the waterfall (LUCA) and the river branches off into multiple branches which then can branch off.

Some rivers can come to an end (extinction).


So a single change (a different LUCA) would possibly mean EVERYTHING would be completely different.

OR maybe this how physics creates all life forms as the only possibility, but that is unlikely, but since we haven't found any other species it is hard to make these predictions, we can only assume based on probability.

Originally Posted by lpetrich

Except that the "arsenic bug" seems to be an unusually arsenic-tolerant organism, but one that nevertheless uses phosphorus in its genetic material: BBC News - Studies refute arsenic bug claim

So, even worse!
When we have all the tech available to figure out what life is doing here we still are capable of getting it wrong, even when we should know better.
Thanks!