Is there life in the universe, and if so has it visited Earth?

[Schrodinger's Dog]

Yeah if possible I'd prefer to stick to the original topic, otherwise it might get a little confusing with some talking about x and the others about y; you can always start another thread about the likelihood of any type of life I suppose.

 

[DaveC426913]

Yes but the OP specifically offers the Drake equation as the basis.

The variables in the Drake equestion need to be determined one at a time without consdieration for subsequent variables. So we have to determine the value for #3 and #4 before we proceed to #5, else we'll skew the results.

 

[SGT]

Yes but the OP specifically offers the Drake equation as the basis.

The variables in the Drake equestion need to be determined one at a time without consdieration for subsequent variables. So we have to determine the value for #3 and #4 before we proceed to #5, else we'll skew the results.

You´re right. Even so, we must consider only reasonably long lasting suns.
Life on Earth began about 1 billion years after the birth of the solar system. Most huge stars don´t live that long.
Dim stars, that constitute about 78% of all suns, don´t output enough energy to allow the complex chemical reactions necessary to life.

 

[Schrodinger's Dog]

Yes but the OP specifically offers the Drake equation as the basis.

The variables in the Drake equestion need to be determined one at a time without consdieration for subsequent variables. So we have to determine the value for #3 and #4 before we proceed to #5, else we'll skew the results.

Fair enough.

 

[SGT]

I just learned about chemical evolution in my cell and molecular biology class. Basically it is believed that Earth's ancient atmosphere, contained inorganic compounds such as nitrogen gas, carbon dioxide, water, hydrogen gas, ammonia, and methane. When you apply electricity to these inorganic compounds in a container, you spontaneously get organic compounds, even amino acids. When you add clay into the picture, which there was a lot of in early earth, scientist have seen the spontaneous synthesis of larger molecules like protiens, and small strands of RNA and DNA. The fact that you can get RNA from having the conditions that were believed to be present in early Earth, is AMAZING because it is believed that RNA was the first self replicating molecule, which gave rise to biological evolution. Now if scientist can create organic molecules from inorganic compounds during an experiment, its going to happen in other parts of the universe that has the right conditions

What I believe is needed for life to evolve is:
1.) Inorganic compounds listed above
2.) A source of energy
3.) Water is essential
4.) And a surface
5.) The planet that has potential for evolution, has to be within a certain range of a star.
6.) A large amount of time in between catastrophic events like asteriod strikes. This is were huge planets like Jupiter come into play. It is believed that Jupiter deflected a lot of asteriod strikes which gave life on Earth time to evolve. I think if the Asteriod that took out the dinosaurs didnt strike earth, this planet would have evolved a reptellian intelligent species, or maybe even a bird like intelligent species. If it wasnt for that perticular asteriod strike that took out the dinosaurs, we would not be here today.

We all agree that there must be abundance of organic compounds in the primeval soup, so oceans are needed.
Clay is only available to the mixture in shallow waters. But those waters must be sporadically in contact with the ocean, which probably means tides.
For large tides to be possible, we need a large satellite, relatively near the planet. From all the planets in the solar system, only Earth and Pluto have such a satellite, but the distance of Pluto to the Sun cancel the other requirements for life.
So, maybe even a planet with abundance of liquid water and enough energy, will not develop life, or develop it very slowly, for lack of a moon like satellite.

I don´t think that a fierce predator, like a dinosaur, would develop intelligence. They don´t need it. For instance, sharks did not evolve substantially in the last 300 million years. There is no evolutionary pressure.
In the other extreme, an herbivore does not have a fast enough metabolism to develop a big brain.
So, I think intelligence is important to a middle sized predator, like primates, dogs or birds as you suggested. But intelligence without manipulative appendages, cannot lead to a technological civilization.
Anyway, without the extinction of dinosaurs, the smaller predators should be hiding and it would be very hard to build a civilization.
But before the extinction of the large reptiles, a more important one happened at the end of the Cambrian, when a large number of marine life disappeared.
It was at the Cambrian that appeared the Pikaia, the first chordate and possible ancestor of all vertebrates. The Pikaia was a small animal (4 cm), surrounded by invertebrate predators, some of them more than a meter long. If those invertebrates had not be extinct, maybe fishes, amphibians, reptiles and mammals would never appear.

 

[DaveC426913]

I don´t think that a fierce predator, like a dinosaur, would develop intelligence. They don´t need it. For instance, sharks did not evolve substantially in the last 300 million years. There is no evolutionary pressure.
In the other extreme, an herbivore does not have a fast enough metabolism to develop a big brain.

1]
There is a continual struggle between predator and prey, a perpetual game of one-upmanship. The prey gets faster or jump higher and the predators have to as well or perish.

Either one will develop intelligence if it gives them an advantage over their counterpart. The prey might get more adaptable to hiding or escaping the predators, or the predators might get more sophisticated and subverting the prey's attempts to remain unseen.

2]
There are two major survival strategies in prehistory: specialization and adaptability.

Animals such as giraffes with their long necks, and koalas, who eat only one food are specialists. They do well when their environement is stable over long periods. They find a niche that works and stick to it. This is a very successful strategy. The problem is, if their environment changes too much, they are doomed.

Dinosaurs and sharks did not develop intelligence because their environments were stable - their hunting techniques continue to work.


Other animals such as humans and rats are opportunists, able to adapt to a changing environment. They are the types that carry on after great upheaval (such as a meteor strike). Soime species do this by being omnivores, or other generalized adaptations, some do it by evolving intelligence that allows their behaviour to adapt to changing circumstances.

Humans were predators just like dinosaurs and sharks, but they lived in a time of great change (eg. the ice age). Being adaptable helped them survive.

 

[SGT]

1]

Humans were predators just like dinosaurs and sharks, but they lived in a time of great change (eg. the ice age). Being adaptable helped them survive.

So did the wolves and the cats, who did not develop intelligence.
My point is that very strong predators don´t need intelligence. Smaller ones do! Wolves are not intelligent, but they have developed group behavior, that makes them more effective in hunting and in protecting themselves.
Lions and tigers, that are more strong predators did not develop group behavior. They are lone hunters, even when living in family, like lions do. A lioness hunts alone and shares the kill with the members of the family, but they don´t have group hunting strategies like wolves.

 

[DaveC426913]

So did the wolves and the cats, who did not develop intelligence.

What on Earth makes you think these animals aren't intelligent?? Cats and dogs are a mere eyeblink behind us in evolutionary terms. In terms of evolutionary traits, I think the degree of intelligence is a matter of splitting hairs.

Are you talking human-level intelligence? Well, if you want to know what happens when there are two competing intelligent species on one planet - ask Neandertal...

 

[Schrodinger's Dog]

What on Earth makes you think these animals aren't intelligent?? Cats and dogs are a mere eyeblink behind us in evolutionary terms. In terms of evolutionary traits, I think the degree of intelligence is a matter of splitting hairs.

Are you talking human-level intelligence? Well, if you want to know what happens when there are two competing intelligent species on one planet - ask Neandertal...

No one really knows why the Neanderthal died out, there has been no evidence of aggressive competition between the Cro-magnon and the Neanderthall, and in fact populations were so small that it would of probably been fairly rare that they even met. The reason they became extinct is hypothesised, some suggest they lacked an ability to adapt to the changing climate post ice age, but no one really knows, suffice to say though, aggresive dispute between two species is not supported by any evidence, and it's hard to see why they would need to fight for land or food anyway.

Well I don't know about him but by intelligent I meant sentient, self aware, capable of sophisticated conscious thought and communication .

 

[DaveC426913]

Well I don't know about him but by intelligent I meant sentient, self aware, capable of sophisticated conscious thought and communication .

All of which apply to higher mammals.

 

[radou]

Lions and tigers, that are more strong predators did not develop group behavior. They are lone hunters, even when living in family, like lions do. A lioness hunts alone and shares the kill with the members of the family, but they don´t have group hunting strategies like wolves.

Interesting, what I heard in a few animal documentaries differs from this pretty much.

 

[Tony11235]

Lions and tigers, that are more strong predators did not develop group behavior. They are lone hunters, even when living in family, like lions do. A lioness hunts alone and shares the kill with the members of the family, but they don´t have group hunting strategies like wolves.

I know this is very off topic, but lions, that is the female groups, DO have hunting strategies. You're right about tigers though. Anyway, back to the topic.

 

[Schrodinger's Dog]

All of which apply to higher mammals.

True but then by sophisticated thought I meant, philosophy and science, and by communication I meant verbal linguistic skills, but seeing as we're talking about animal life atm, it wasn't really relevant.

AFAIK only chimps and dolphins have shown evidence of self awareness, and even then the evidence is disputed.

Predators are smarter than prey, they also usual have sophisticated social structures and highly competative infrastructures, which many herd animals lack, I think it's safe to say that predatory animals would be more likely to develop intelligence, although I'm of course only basing that on Earth life, hunting takes some real co-operative skills also.

 

[DaveC426913]

I think you're splitting evolutionary-scale hairs here. Suggesting mammals aren't quite intelligent is a highly humanocentric bias. Compared to the other 99.9999999% of the biomass on the planet, mammals are rocket surgeons.

 

[Ivan Seeking]

Rocket surgeons?

 

[SGT]

I think you're splitting evolutionary-scale hairs here. Suggesting mammals aren't quite intelligent is a highly humanocentric bias. Compared to the other 99.9999999% of the biomass on the planet, mammals are rocket surgeons.

Octopi can open a closed jar to pick a crab that is inside. Not many mammals can do that.

 

[DaveC426913]

Octopi can open a closed jar to pick a crab that is inside. Not many mammals can do that.

Certainly. Which is why octopi are so fascinating for their oddball convergent trait of intelligence.

 

[Schrodinger's Dog]

Octopi can open a closed jar to pick a crab that is inside. Not many mammals can do that.

I think generally sea life has a much better chance at achieving technology if it migrates to land, again this is obviously a humanocentric idea, but I can see where it might be generally applicable, due to the nature of the environment over waters environment.

Intelligence can form in the sea and indeed life is most likely to form there, but the chances of octopuses building an advanced technology? Is it as good as say Chimps assuming man disappears off the scene? Who's the most likely species to form an intelligent, sapient, verbally communicating, scientific society?

Water is vital, but In my mind planets with both water and land, not only have an abundance of water for basic life forming, but have land to provide a more conducive environment for intelligent life formation. Thus I personally think the best chance of speciation comes from a land, water planet.

 

[SGT]

I think generally sea life has a much better chance at achieving technology if it migrates to land, again this is obviously a humanocentric idea, but I can see where it might be generally applicable, due to the nature of the environment over waters environment.

Intelligence can form in the sea and indeed life is most likely to form there, but the chances of octopuses building an advanced technology? Is it as good as say Chimps assuming man disappears off the scene? Who's the most likely species to form an intelligent, sapient, verbally communicating, scientific society?

Water is vital, but In my mind planets with both water and land, not only have an abundance of water for basic life forming, but have land to provide a more conducive environment for intelligent life formation. Thus I personally think the best chance of speciation comes from a land, water planet.

I agree with you, simply by the fact that the development of metallurgy is impossible in an aquatic environment and without metallurgy a technological civilization is impossible.
I only mentioned octopuses because of Dave´s affirmation that mammals are smarter than all other life forms.
It seems that dolphins are as intelligent as chimps, but in the absence of mankind, chimps are more likely to rule the planet than dolphins. Chimps have prehensile limbs and live on firm ground, where in a few million years they could perhaps develop a civilization.

 

[DaveC426913]

I only mentioned octopuses because of Dave´s affirmation that mammals are smarter than all other life forms.

Not quite what I said but who's counting...

 

[SGT]

Not quite what I said but who's counting...

Compared to the other 99.9999999% of the biomass on the planet, mammals are rocket surgeons.

Could you please inform us what do you mean by the other 99.9999999% of the biomass on the planet?

 

[Schrodinger's Dog]

Could you please inform us what do you mean by the other 99.9999999% of the biomass on the planet?

I think he clearly means every other non mammalian species in the Domains of Bacteria, Archea and Eukaryota.

These guys excluding mammals in bold:-

http://en.wikipedia.org/wiki/Species

http://en.wikipedia.org/wiki/Image:Phylogenetic_tree.svg

As a soft guide, however, the numbers of identified species as of 2004 can be broken down as follows: [3]

Species list follows.

* 287,655 plants, including:
o 15,000 mosses,
o 13,025 ferns,
o 980 gymnosperms,
o 199,350 dicotyledons,
o 59,300 monocotyledons;
* 74,000-120,000 fungi[1];
* 10,000 lichens;
* 1,250,000 animals, including:
o 1,190,200 invertebrates:
+ 950,000 insects,
+ 70,000 molluscs,
+ 40,000 crustaceans,
+ 130,200 others;
o 58,808 vertebrates:
+ 29,300 fish,
+ 5,743 amphibians,
+ 8,240 reptiles,
+ 9,934 birds,
+ 5,416 mammals.

However the total number of species for some phyla may be much higher:

* 5-10 million bacteria[2];
* 1.5 million fungi[1];

 

[DaveC426913]

Could you please inform us what do you mean by the other 99.9999999% of the biomass on the planet?

as in: not all. There are some exceptions, such as Octopi and some birds that rival mammals in their intelligence.

Splitting hairs, but I didn't want to be misquoted.

 

[DaveC426913]

I think he clearly means every other non mammalian species in the Domains of Bacteria, Archea and Eukaryota.

These guys excluding mammals in bold:-

http://en.wikipedia.org/wiki/Species

Where did you get these numbers from? I don't see them in the Wiki article. It would be cool to see them as a pie chart.

It would be even cooler to see them as a cylinder chart - with the height of the pies representing actual estimated Earth biomass in grams. You'd have a volumetric representation of all life on Earth broken down by quantity and species. I'll bet mammals would be a pinprick.

 

[Schrodinger's Dog]

Where did you get these numbers from? I don't see them in the Wiki article. It would be cool to see them as a pie chart.

It would be even cooler to see them as a cylinder chart - with the height of the pies representing actual estimated Earth biomass in grams. You'd have a volumetric representation of all life on Earth broken down by quantity and species. I'll bet mammals would be a pinprick.

They're there check out the wiki link again. I'm surprised you didn't see them.

http://en.wikipedia.org/wiki/SpeciesLook under the heading species then binomials they're next.

 

[DaveC426913]

I'm surprised you didn't see them.

As am I...

 

[Ivan Seeking]

A friend recently attended a lecture by Janice Voss, during which she was asked how many earthlike planets they expect to find within four to six years via the Kepler mission. She responded by saying that they expect to find thousands.

I have a really cool Power Point presentation made during her five shuttle missions, that she is handing out, but no way to post it.

 

[verdigris]

Until someone explains how self-replicating DNA molecules came into existence involving the kind of chemical reactions we know can exist on Earth then the answer has to be maybe to extraterrestrials visiting Earth.

 

[SGT]

Until someone explains how self-replicating DNA molecules came into existence involving the kind of chemical reactions we know can exist on Earth then the answer has to be maybe to extraterrestrials visiting Earth.

This only transfers the problem. How did those molecules come in existence elsewere?

 

[Ivan Seeking]

Posts deleted: As per the S&D posting guidelines, please keep in mind that we can speculate about the possiblity of life, but not the motives of any alleged visitors. We could speculate on motives if shown proof of a visitation.