60 years of silence - so far

[lpetrich]

Looking at the literature on other species, we find evidence of some of the Big Five personality factors in their personality variations.

Openness was not researched very clearly, though curiosity may qualify.

Conscientiousness we share with chimps and no other species observed in detail. For chimps, it is evident as being attentive and directed toward some goal, with an opposite of being erratic, unpredictable, and disorganized.

Agreeableness is found across placental mammals, often as friendliness vs. aggressiveness: our species, chimp, gorilla, rhesus and vervet monkeys, rat, dog, cat, hyena, horse, donkey, pig, elephant.

There was a study that found neuroticism variation in kangaroos, as vigilance in looking for predators, but I couldn't find much more. I couldn't find anything on personality variation in chickens or iguanas, for instance.

Extraversion and neuroticism are found among all species tested, extraversion often as assertiveness or boldness, neuroticism often as sensitivity to threat. Placentals, parrot, rook bird, lizard, turtle, guppy, cricket, aphid, paper wasp, hermit crab, octopus, land snail.

That covers all of Bilateria, the bilaterally-symmetric animals. Bilaterians all have dopamine-like and serotonin-like neurotransmitters, and these are connected to assertiveness (extraversion) and sensitivity (neuroticism) variations where such connections have been investigated.

Looking further, cnidarians (sea anemones, jellyfish, etc.) also have dopamine-like and serotonin-like neurotransmitters, but comb jellies and sea sponges don't.

So neural circuits for assertiveness and sensitivity go very far back, almost as far back as the origin of the nervous system itself.

 

[bilby]

An exoplanet without life would not be expected to have an oxygen rich atmosphere; Conversely, an exoplanet with alien life could easily have an atmosphere that is rich, not only in oxygen, but also in other unstable toxic chemicals, such as (for example) chlorine.

Some scientists claim (outlining three scenarios) that lifeless planets might have an oxygen atmosphere.

None of these scenarios are able to sustain such an atmosphere though. There might be oxygen produced, but as the amounts would be dramatically lower than the ongoing amount produced by photosynthesis, the resulting atmosphere would have a few percent of O₂ at best.

Venus is a pretty good match for their first scenario, yet has essentially zero oxygen, not bound to either carbon or sulphur, in her atmosphere.

Oxygen production in all three environments I would expect to be more than offset by weathering of minerals; I am unconvinced that even an absence of crustal turnover through plate tectonics could be sufficient to allow a sizeable proportion of atmospheric O₂ to arise.

Oxygen is just too reactive to hang around - it needs constant and massive replenishment to achieve double digit percentages of it in the atmosphere.

 

[Jimmy Higgins]

And without a doubt, it is happening elsewhere. Ignoring the whole, well there are also other issues other than air when it comes to living on another planet, the distance (and maybe even more importantly, the direction) to elsewhere, those are the issues. There are almost certainly millions of places that mimic Earth. Maybe billions! But getting across the vacuum to live there? Sounds kind of awful. Imagine a generation ship where you can't withstand population growth or decline (or the outdoors).

This is our rock. And it might as well be the only rock based on the boundary conditions on getting anywhere else.

 

[steve_bank]

If you look at the fossil record and marine and surface life today as a species we are one of many.

Even if there are Earth like worlds and life begins the genetics that give rise to science and technology may be remote.

North, Cereal, and South American cultures had the capacity but never developed science and technology on a par with other continents.

Occam's Razor? Maybe we are not detecting anything because there is nothing to detect,

 

[Jimmy Higgins]

If you look at the fossil record and marine and surface life today as a species we are one of many.

That is a bit overly simplistic. Yes, life is abundant on Earth. In fact, we have a massive ecosystem that relies on, for the most part, itself to exist. There is a balance. There is no evidence to suggest that living on another planet could be possible. The air, gravity, radiation all could be perfect, but the viruses, bacteria, microbes, we aren't adapted to. Europeans went to North America and killed off a lot of people just through disease. And how our presence in the new eco-system could then impact that eco-system itself. Granted, it should be impossible to move enough of us over to the planet to cause such an issue (which it in itself makes space travel seem silly).

Even if there are Earth like worlds and life begins the genetics that give rise to science and technology may be remote.

North, Cereal, and South American cultures had the capacity but never developed science and technology on a par with other continents.

You mean after the Spanish wiped out the Aztecs, Mayans, and Incans, destroying their art, culture, and agriculture?

Occam's Razor? Maybe we are not detecting anything because there is nothing to detect,

It is seemingly impossible for intelligent life to only exist on one planet in the entire universe. But just because it exists elsewhere doesn't mean we can contact it or detect it.

 

[Elixir]

You mean after the Spanish wiped out the Aztecs, Mayans, and Incans, destroying their art, culture, and agriculture?

Oh snap.
Right. Just after that. Go figure.

 

[pood]

Tantalizing sign of possible life on a faraway world

 

[steve_bank]

No, I meant before the Europeans. Incas were good civil engineers, at least as good as the Romans. But there did not seem to be a scientific inquisitiveness as the Greeks, Romans, Chinese, and others.

And the cultures were as aggressive, territorial, and violent as the Europeans. Europeans had better technology and weapons.

There is nothing to say a human like ET would develop technology.

What is the definition of 'intelligent'? Us intelligent humans any well destroy the ecosystem well before the predicted sun's life cycle makes life impossible. We generally equate intelligence with tool making.

My point is that an ecosystem may be teeming with life, but that does not mean there would necessarily be a species capable of developing technology.

If dinos did mot diminish would we be here?

If our ecosystem including humans is a norm, then if there were a lot of space faring ETs there would be conflict. Colonization and explotaion of resources. In our ecosystem all living things compete for resources. Even plants, albeit in slow motion.

When we dream of ETs like us it is a case of be careful what you ask for you might get it.

What does ET call humans in a space capsule? Spam in a can? A snack?

There are bacteria in deep mines that digest rock. Life at undea vents that live in toxic environments to us. Bacteria was found living in high radiation in a Chernobyl reactor.

Depnding on how you define life it may be plentiful.

 

[pood]

HIghly unlikely humans would be able to eat ET or vice versa.

 

[steve_bank]

Correction, fungus not bacteria.

Radiotrophic fungus - Wikipedia

en.wikipedia.org

Radiotrophic fungi are fungi that can perform the hypothetical biological process called radiosynthesis, which means using ionizing radiation as an energy source to drive metabolism. It has been claimed that radiotrophic fungi have been found in extreme environments such as in the Chernobyl Nuclear Power Plant.

Most radiotrophic fungi use melanin in some capacity to survive.[1] The process of using radiation and melanin for energy has been termed radiosynthesis, and is thought to be analogous to anaerobic respiration.[2] However, it is not known if multi-step processes such as photosynthesis or chemosynthesis are used in radiosynthesis or even if radiosynthesis exists in living organisms.

Discovery

Many fungi have been isolated from the area around the destroyed Chernobyl Nuclear Power Plant, some of which have been observed directing their growth of hyphae toward radioactive graphite from the disaster, a phenomenon called “radiotropism”.[3] Study has ruled out the presence of carbon as the resource attracting the fungal colonies, and in fact concluded that some fungi will preferentially grow in the direction of the source of beta and gamma ionizing radiation, but were not able to identify the biological mechanism behind this effect.[4] It has also been observed that other melanin-rich fungi were discovered in the cooling water from some other, working, nuclear reactors. The light-absorbing compound in the fungus cell membranes had the effect of turning the water black.[5] While there are many cases of extremophiles (organisms that can live in severe conditions such as that of the radioactive power plant), a hypothetical radiotrophic fungus would grow because of the radiation, rather than in spite of it.[6]

Further research conducted at the Albert Einstein College of Medicine showed that three melanin-containing fungi—Cladosporium sphaerospermum, Wangiella dermatitidis, and Cryptococcus neoformans—increased in biomass and accumulated acetate faster in an environment in which the radiation level was 500 times higher than in the normal environment. C. sphaerospermum in particular was chosen due to this species being found in the reactor at Chernobyl. Exposure of C. neoformans cells to these radiation levels rapidly (within 20–40 minutes of exposure) altered the chemical properties of its melanin, and increased melanin-mediated rates of electron transfer (measured as reduction of ferricyanide by NADH) three- to four-fold compared with unexposed cells. However, each culture was performed with at least limited nutrients provided to each fungus. The increase in biomass and other effects could be caused either by the cells directly deriving energy from ionizing radiation, or by the radiation allowing the cells to utilize traditional nutrients either more efficiently or more rapidly.[6]

Outside of the fungal studies, similar effects on melanin electron-transport capability were observed by the authors after exposure to non-ionizing radiation. The authors did not conclude whether light or heat radiation would have a similar effect on living fungal cells.[6]

Why not ET with a taste for humans?

 

[Jokodo]

No, I meant before the Europeans. Incas were good civil engineers, at least as good as the Romans. But there did not seem to be a scientific inquisitiveness as the Greeks, Romans, Chinese, and others.

And the cultures were as aggressive, territorial, and violent as the Europeans. Europeans had better technology and weapons.

Yes, Western Europeans had Hittite (i.e., Anatolian) iron and wheat, Chinese gunpowder, and horses that were first domesticated somewhere between Ukraine and Kazakhstan.

They did invent cabbage soup, though.

 

[steve_bank]

Maybe humans would be stuffed and disposed in an ET museum. Disected in school biolgy classess like we do frogs.

Many possibities have been covered in scifi.

 

[Loren Pechtel]

If you look at the fossil record and marine and surface life today as a species we are one of many.

Even if there are Earth like worlds and life begins the genetics that give rise to science and technology may be remote.

North, Cereal, and South American cultures had the capacity but never developed science and technology on a par with other continents.

Occam's Razor? Maybe we are not detecting anything because there is nothing to detect,

1) Ever read Guns, Germs, and Steel? Even if he's not entirely correct there is at least some truth to the situation. Europe was in the best position to advance.

2) Somebody had to be first. The fact that someone was doesn't say that the others wouldn't have in time.

 

[DBT]

Survive the Great Filter and who knows what is possible.

 

[steve_bank]

Back in the 90s the guy who did the Survivor Man series spent time with a South American aborigine group.

They were not completely isolated and had some trade with the outside world. Making and maintaining hunting weapons and hunting/gathering were full time occupations.

They lived in small clusters. When one group traveled to visit another they were continually foraging and looking for game.

One thing Sub Saharan Africa lacked was natural harbors and acess from the inerior to the coast. Look along the coasts of the USA and Europe and you will see harbors and navigable rivers.

For a class of thinkers to exist there has to be an excess of food.

Many variables for an ET to evolve technology which can not be quantified.

In human history it was water and a stable food supply that allowed initial growth.

There is nothing to say that an ET species with the potential for technology will develop technology.

There may be many, or we maybe the one and only for all time.

 

[lpetrich]

There is a proposal for defining such a division of geological time:  Anthropocene and Scientists Search For The Anthropocene : NPR and What Is the Anthropocene and Are We in It? | Science| Smithsonian Magazine and What is the Anthropocene and why does it matter? | Natural History Museum

There is a lot of controversy over which geological marker to use, and what would count as the beginning of such a division of geological time.

 Geologic time scale

• Phanerozoic Eon -- 538.8 Mya -- trace fossil Treptichnus pedum -- likely worm burrows
• Cenozoic Era -- 66.0 Mya -- K-Pg mass-extinction iridium spike -- likely from an asteroid impact
• Quaternary Period -- 2.56 Mya -- beginning of the geologically recent ice ages
• Holocene Epoch -- 11.7 kya -- end of the Younger Dryas cold period
• Meghalayan Age -- 4.2 kya -- beginning of 200-year drought

Will the Anthropocene be comparable to the Holocene? The Meghalayan?

I thought of alternatives related to radiation and to CO2 (smoke). So I went to wiktionary.org and I considered what might be good Latin-derived or Greek-derived terms.

Ray-smoke:
(Latin) Radiofumic
(Greek) Actinocapnic

 

[lpetrich]

A big problem with evolution is that it takes place much slower than it might be taking place, judging from episodes of rapid evolution.

How gradual is evolution? It's long been claimed that the evolution of life is a very gradual process. But gradualism can be hard to find in the fossil record, and in 1972, Niles Eldredge and Stephen Jay Gould proposed an alternative, which they called "punctuated equilibrium" sometimes abbreviated punc-eq.

They considered some theorizing on how new species emerge ("speciation"), and they decided that the fossil record fits a pattern of bursts of evolution in small populations, bursts that produce offshoot species, species that then do not change very much after their origin, at least in fossilizable phenotypes.

That explains the lack of gradualism that is often observed -- species often never changing very much in fossilizable phenotype.

But it has further problems, like what makes these offshoots and bursts relatively rare? Or at least successful ones, because many of them may quickly go extinct for various reasons.

Punctuated equilibria - Scholarpedia

 

[lpetrich]

Stromatolites are mats of sediment that are stuck onto microbial biofilms, notably from cyanobacteria. They are the oldest known fossils, and they became common in the fossil record. They became rare in the early Paleozoic, however, from the emergence of animals that could efficiently eat them.

 Stromatolite

Advanced two- and three-dimensional insights into Earth's oldest stromatolites (ca. 3.5 Ga): Prospects for the search for life on Mars | Geology | GeoScienceWorld

Cyanobacteria evolution: Insight from the fossil record - PMC -- some Proterozoic fossil cyanobacteria have some resemblance to various present-day ones.

Frontiers | An Expanded Ribosomal Phylogeny of Cyanobacteria Supports a Deep Placement of Plastids

Frontiers | Evolutionary Patterns of Thylakoid Architecture in Cyanobacteria

 Gloeobacter -- that one diverged from the other cyanobacteria some 3 billion years ago. Its main distinction from other cyanobacteria is where its photosynthetic apparatus is located: on the cell membrane. That's where electron-transfer energy-metabolism systems are almost always located. But most other cyanobacteria have their photosynthetic apparatus located in structures inside their cells: thylakoids. These likely originated as inpouchings of the cells' membranes.

 

[lpetrich]

The evolutionary diversification of cyanobacteria: Molecular–phylogenetic and paleontological perspectives | PNAS

Unlike most other bacteria, some filamentous cyanobacteria evolved a degree of cell differentiation, producing both specialized cells for nitrogen fixation (heterocysts) and resting cells able to endure environmental stress (akinetes). Phylogenetic analyses support the hypothesis that cyanobacteria capable of cell differentiation are monophyletic, and the geological record provides both upper and lower bounds on the origin of this clade. Fossil akinetes have been identified in 1,650- to 1,400-mega-annum (Ma) cherts from Siberia, China, and Australia, and what may be the earliest known akinetes are preserved in ≈2,100-Ma chert from West Africa. Geochemical evidence suggests that oxygen first reached levels that would compromise nitrogen fixation (and hence select for heterocyst differentiation) 2,450–2,320 Ma. Integrating phylogenetic analyses and geological data, we suggest that the clade of cyanobacteria marked by cell differentiation diverged once between 2,450 and 2,100 Ma, providing an internal bacterial calibration point for studies of molecular evolution in early organisms.

Evolution of multicellularity coincided with increased diversification of cyanobacteria and the Great Oxidation Event | PNAS

Cyanobacteria are among the most diverse prokaryotic phyla, with morphotypes ranging from unicellular to multicellular filamentous forms, including those able to terminally (i.e., irreversibly) differentiate in form and function. It has been suggested that cyanobacteria raised oxygen levels in the atmosphere around 2.45–2.32 billion y ago during the Great Oxidation Event (GOE), hence dramatically changing life on the planet. However, little is known about the temporal evolution of cyanobacterial lineages, and possible interplay between the origin of multicellularity, diversification of cyanobacteria, and the rise of atmospheric oxygen. We estimated divergence times of extant cyanobacterial lineages under Bayesian relaxed clocks for a dataset of 16S rRNA sequences representing the entire known diversity of this phylum. We tested whether the evolution of multicellularity overlaps with the GOE, and whether multicellularity is associated with significant shifts in diversification rates in cyanobacteria. Our results indicate an origin of cyanobacteria before the rise of atmospheric oxygen. The evolution of multicellular forms coincides with the onset of the GOE and an increase in diversification rates. These results suggest that multicellularity could have played a key role in triggering cyanobacterial evolution around the GOE.

So it took some 500 million years before cyanobacteria started making thylakoids. Could thylakoids have helped by increasing the total amount of the photosynthetic parts? Or helped by making those parts less vulnerable to the external environment?

 

[lpetrich]

 Eukaryogenesis - the first eukaryotes originated around 2 billion years ago, as cyanobacteria produced enough oxygen to produce the Great Oxidation Event of around then. This made it feasible to combine oxygen with biological molecules to extract energy, and one microbe that did that got together with some other microbes, making the first eukaryote.

The first possible fossils of eukaryotes are called "acritarchs", because it's hard to pin down what they are fossils of. Palaeos Proterozoic: The Proterozoic Era -- They don't have a lot of variation in them before about a billion years ago, and after that, they do.

Also around a billion years ago is the oldest known fossil of a red alga, Bangiomorpha pubescens, and of a green alga, Proterocladus antiquus. That means that red algae and green algae had diverged before then. Bangiomorpha was named from its close resemblance to some present-day red algae, the bangiophytes.

The Proterozoic Record of Eukaryotes | Paleobiology | Cambridge Core

 Ediacaran biota - lots of odd organisms that started showing up around 580 Mya (million years ago). Soon after, at 575 Mya, was the  Avalon explosion of organisms. Many Ediacaran organisms do not have any recognizable relationship with later ones, and are sometimes classified as  Vendobionda using an earlier name for the Ediacaran: Vendian.

These organisms suffered a mass extinction at the base of the Cambrian, 538.8 Mya, though some of them survived into the Cambrian.