The Impossibility of Intelligent Life

[Keln]

I was reading an article the other day discussing the possibility of ever finding intelligent life elsewhere in the universe, and I was wondering about what conditions really do matter for intelligent, technologically advanced life. By technologically advanced, I mean basic Stone Age technology at the very least, not necessarily even modern technology. I've seen a lot of arguments that life might be completely different elsewhere and not even need such as liquid water or even oxygen in meaningful amounts.

But that concept bugs me a bit. Looking at life here on Earth, it seems to me that all life has evolved on a rather ideal planet, at an ideal distance from an ideal star, within an ideal region of an ideal galaxy, located in an ideal galactic neighborhood in an ideal universe that had the perfect set of parameters to even allow for baryonic matter.

That's an awful lot of perfect that has to fall into place to allow for not just life, but intelligent life to form.

The reason the argument for very different types of intelligent life bugs me is the idea that water and oxygen might not be necessary for such life. Granted, there could be lifeforms that are silicon-based or what-have-you, but water is a rather special chemical. I guess my questions are:

• Is there a chemical analogue for water? Is there anything that could substitute it biologically? And could any such analogue exist under different planetary conditions as a liquid?

• Is there a possibility for fire without a significant amount of atmospheric oxygen? What else could be an "oxidizer"? I figure fire would be key for a civilization.

• Is it really feasible for life to form if too close (higher radiation) or too far (less energy) to/from a star? Could the "Goldilocks Zone" have more to it than just enough heat for liquid water?

• Does the type of water matter? If there were water on a planet that had a much higher concentration of Deuterium, would that biologically matter?

• If the answer to all of the above were to point to an Earth-like type planet, does that still leave billions of possibilities, or does that really cut out the chance that intelligent life could have formed elsewhere? Could the Earth actually be special?

 

[Bystander]

"Goldilocks Zone"

You might want to take a look at cosmic abundances of elements.

Earth actually be special?

Earth sized planets with earth-type compositions and chemistries are going to be quite common.

 

[Czcibor]

But that concept bugs me a bit. Looking at life here on Earth, it seems to me that all life has evolved on a rather ideal planet, at an ideal distance from an ideal star, within an ideal region of an ideal galaxy, located in an ideal galactic neighborhood in an ideal universe that had the perfect set of parameters to even allow for baryonic matter.

Intelligent design? ;)

And more seriously if life is possible one planet per million, then those who live on the lucky planet feel superior. On the remaining 999 999 planets there is no one to be worried about.

(I agree, there is a problem how to deal with lucky enough laws of physics)

• Is there a chemical analogue for water? Is there anything that could substitute it biologically? And could any such analogue exist under different planetary conditions as a liquid?

The guesses are:
http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry#Non-water_solvents

(there are solvents that look not bad, the tricky part is whether there is a place to build whole complicated biochemistry)

• Is there a possibility for fire without a significant amount of atmospheric oxygen? What else could be an "oxidizer"? I figure fire would be key for a civilization.

It seems (based on evolution on Earth) that carbon based life needs high concentration of oxygen to seriously let multicelular organisms to evolve:
http://en.wikipedia.org/wiki/Great_Oxygenation_Event

• Is it really feasible for life to form if too close (higher radiation) or too far (less energy) to/from a star? Could the "Goldilocks Zone" have more to it than just enough heat for liquid water?

There are ideas of tidal heating in exomoons.
http://en.wikipedia.org/wiki/Europa_(moon)#Potential_for_extraterrestrial_life
Just I fail to imagine aquatic creatures there trying to build a civilization. There might be problems with food storage, not mentioning fire ;)

(non carbon based life should have different expectations)

• Does the type of water matter? If there were water on a planet that had a much higher concentration of Deuterium, would that biologically matter?

I'd guess that's something what can worked around by evolution, just enzymes would have to have a bit different properties.

By occasion - let's imagine creatures living on a tidally locked planet, wondering whether intelligent life can evolve in so adverse and changing conditions where there is life/day cycle and seasons. :D

 

[Bandersnatch]

But that concept bugs me a bit. Looking at life here on Earth, it seems to me that all life has evolved on a rather ideal planet, at an ideal distance from an ideal star, within an ideal region of an ideal galaxy, located in an ideal galactic neighborhood in an ideal universe that had the perfect set of parameters to even allow for baryonic matter.

That's an awful lot of perfect that has to fall into place to allow for not just life, but intelligent life to form.

This is the old puddle in a hole argument. Of course we're reasonably well-adapted to existence on Earth - we've evolved here. I don't know about the environment being ideal - the extinct 99.99% of species would probably disagree.

This is a wholly pointless speculation. We've got one sample of life-bearing planet with one sample of species we call intelligent (by which we mean 'exactly like us'). There's too little data available to make sweeping generalisations about the possibility of extraterrestrial life, let alone intelligence.

 

[SteamKing]

This is the old puddle in a hole argument. Of course we're reasonably well-adapted to existence on Earth - we've evolved here. I don't know about the environment being ideal - the extinct 99.99% of species would probably disagree.

Well, for all those extinct species, there was a time when the environment was ideal for them ... until it wasn't, which is why they are no longer with us. :L

We take for granted that what went on yesterday will continue tomorrow, and that's just wishful thinking.

The dinosaurs thrived and flourished for 150 million years and then were gone in an instant, in geological terms. Yet, even over that vast span, there is no indication that dinosaurs ever evolved any more intelligence or instinct than was needed to survive and produce the next generation.

It appears that what drove the evolution of what we humans call intelligence was a combination of factors in just the right proportions. The environment of our distant ancestors changed, but not so abruptly or completely that there was insufficient time for survivors to move to better surroundings and adapt to them.

Even should all the factors on a given planet be conducive to the evolution of intelligent life, it all depends on a number of factors external to that planet. After all, it takes just one asteroid collision to wipe out millions, if not billions, of years of existence. Just ask the dinosaurs. ;)

 

[JLowe]

What's odd to me is that the only place we know life exists, it exists in a phenomenal number of ways including sentience. It's highly likely no other life exists in the solar system, and if it does its going to be exceptionally hard to find. The fact that this planet was inhabited by life far longer than it was intelligent life, should imply the likelihood of finding simple life greater than that of finding intelligent life, but so far we've not found a single cell of any form of life outside the planet.

If we fail to find some fossilized evidence of life on mars, then IMO it doesn't bode well for the possibility of ever finding life anywhere. Not impossible, but highly unlikely given the massive distances of space and fact that Mars appears the second most habitable place in the solar sytem.

 

[Travis_King]

I guess the main point to raise here is that "intelligence" isn't necessarily the apex of evolution. Asking, "What are the odds of finding intelligent life?" is, to some extent, similar to asking, "What are the odds of finding life-forms which use echo-location?"

Intelligent life exists here because one of the life forms evolved a higher capacity for forethought (and memory) and communication. There is no intrinsic need for intelligent life, therefore there is no real reason to expect it to be common at all among any inhabited planets out there.

 

[StatGuy2000]

What's odd to me is that the only place we know life exists, it exists in a phenomenal number of ways including sentience. It's highly likely no other life exists in the solar system, and if it does its going to be exceptionally hard to find. The fact that this planet was inhabited by life far longer than it was intelligent life, should imply the likelihood of finding simple life greater than that of finding intelligent life, but so far we've not found a single cell of any form of life outside the planet.

If we fail to find some fossilized evidence of life on mars, then IMO it doesn't bode well for the possibility of ever finding life anywhere. Not impossible, but highly unlikely given the massive distances of space and fact that Mars appears the second most habitable place in the solar sytem.

Limiting our discussion to the chance of finding life in any form (rather than intelligent life), it may well be the case that the probability that we will encounter such life within our solar system is indeed quite small. However, it is worth keeping in mind that there are many other solar systems other than the one we are in (billions of them). The questions would be the following:

(1) Are conditions in Earth so exceptional or unusual that the probability of findings planets with similar characteristics in other solar systems is very small?

(2) Can a slightly different configuration of the plant or solar system affect the probability of the existence of life in other solar systems?

Question (1) is currently impossible to answer without knowing more about the characteristics of planets in other solar systems. The early indications based on observations from robotic probes is that planets like Earth (i.e. those possessing carbon, and possibly liquid water), may not be all that unusual in other solar systems, so at least there is the possibility that life could emerge there.

Question (2) is currently also impossible to answer.

 

[Czcibor]

I was reading an article the other day discussing the possibility of ever finding intelligent life elsewhere in the universe,

I've just found one more challenge in your question: "finding". What counts as finding? I mean if let's say there is one intelligent civilization per a few galaxies, then finding them would be quite tricky.

This is a wholly pointless speculation.

Not wholly - it's possible to make here a summary of what we know, even if this summary would be terribly short.
Before Wolszczan publication concerning pulsar planets in 1992 whole discussion concerning exoplanets could have been stopped in the same manner.

 

[JLowe]

Limiting our discussion to the chance of finding life in any form (rather than intelligent life), it may well be the case that the probability that we will encounter such life within our solar system is indeed quite small. However, it is worth keeping in mind that there are many other solar systems other than the one we are in (billions of them). The questions would be the following:

(1) Are conditions in Earth so exceptional or unusual that the probability of findings planets with similar characteristics in other solar systems is very small?

(2) Can a slightly different configuration of the plant or solar system affect the probability of the existence of life in other solar systems?

Question (1) is currently impossible to answer without knowing more about the characteristics of planets in other solar systems. The early indications based on observations from robotic probes is that planets like Earth (i.e. those possessing carbon, and possibly liquid water), may not be all that unusual in other solar systems, so at least there is the possibility that life could emerge there.

Question (2) is currently also impossible to answer.

Yes I understand that, my point was that the distance of space, in those cases, are so massive that the chance we find life there are very small.

If it's announced tomorrow that an exo planet of roughly Earth size is found to have oxygen in its atmosphere and lie within the goldilocks zone, it still would not prove the existence life there. It would almost require the planet have intelligent life of its own to also detect our planet and we mutually send signals to each other.

That's just incredibly unlikely to happen.

 

[Keln]

I've just found one more challenge in your question: "finding". What counts as finding? I mean if let's say there is one intelligent civilization per a few galaxies, then finding them would be quite tricky.

Granted, but "finding" isn't important to my questions. I recognize that the universe could teem with life and we'd still never find it. I'm more interested in what it truly takes for a sentient form of life which can form a basic civilization to emerge on a planet.

 

[Drakkith]

Granted, but "finding" isn't important to my questions. I recognize that the universe could teem with life and we'd still never find it. I'm more interested in what it truly takes for a sentient form of life which can form a basic civilization to emerge on a planet.

Unfortunately we only have 1 species to look at, so there's no telling.

 

[Nathanael]

I'm more interested in what it truly takes for a sentient form of life which can form a basic civilization to emerge on a planet.

What is civilization? We may have ideas of what civilization is, but can we define the word universally? What really makes a civilization a civilization?

I will explain what I think defines a civilization. To me it seems there is one main difference between the civilized and uncivilized worlds. Prior to civilization, every individual was independent. That is, when we were uncivilized 'hunters and gatherers,' every person was an expert at the entire culture. Every man knew how to hunt, cook, build, make clothes and tools, etc. But when civilization arose, independence was lost and everyone became largely dependent on everyone else. The advantage of this was that individuals became more specialized. Instead of everyone being an expert in everything, some people became experts in some things and others were experts in other things. Independence was traded for specialization. This, as we can clearly see, opened up a lot of potential for development.

When I try to transcend our familiar human anecdote to define civilization universally, I come to the following general idea: Civilization is where a collection of individuals becomes dependent on each other by splitting up into groups of specialized functions. This enables more potential for growth than if each individual survived independently.
This is just my perspective on the essence of civilization, so feel free to improve on it, or to propose alternate definitions of what you are looking for.

One other example jumps out at me from this definition. Cells. Our cells have come together to form our bodies, and different groups of cells perform different functions, but all are dependent on all. (The heart couldn't live without the stomach and vice versa and etc.) So are cells considered a civilization? If not, then what is the requirement which they do not satisfy? (In other words, how do you define civilization?)

Individual cells are to the human body as individual humans are to (civilized) humanity. The more I think about this analogy, the more aspects of it I find. Look at how much more potential the human body has compared with trillions of cells which survive independently. Look at how much more potential the human species has compared with billions of humans surviving independently. It almost seems like "civilization" is a natural progression of this living world.

 

[mousemat]

Here is my take on this.
Firstly, look at how fast our civilization has developed in the last 10000 years. It's insanely fast compared to the lifetime of the universe. And then look at how our technology is advancing. It's advancing at an exponential rate. In the next 10000 years, we will definitely become a multi-planetary species, provided we don't wipe ourselves out. Who knows how advanced we will be.
Assuming there is life out there, it will be either more intelligent or less intelligent than us.
In the case that is is more intelligent, using our observation of our advancement of society, wouldn't it be fair to conclude that the intelligent life is extremely intelligent and vastly more advanced than us? 10000 years is a very short span, it is very very unlikely that there is a similar species advancing at the same pace as us. Thus, if it was an extremely intelligent species will it not have probably expanded outwards and displayed observable signs of it's existence?
In the case that it is less intelligent, there are two scenarios.
1. It is simple life, which is not the focus of this discussion.
2. It is "stone age" intelligent. My argument here is the length of the stone age (3.4 million years) is only 0.0002 % of the universe's estimated lifetime. It's only a sample size of 1, but that's all we've got. If intelligent life only takes about 3.4 million years (plus minus tens of millions of years, its still tiny in comparison to the lifetime of the universe) to develop to become a highly intelligent species, there is a very low chance that intelligent life lies in the universe that has not developed into a highly intelligent species.

Just my 2 cents, feel free to refute.

 

[256bits]

Granted, but "finding" isn't important to my questions. I recognize that the universe could teem with life and we'd still never find it. I'm more interested in what it truly takes for a sentient form of life which can form a basic civilization to emerge on a planet.

That is a quite open ended question I think. You yourself could probably make a list right now of several basic features that you think a species would need to possesses in order to at least have the capability to form a civilization. One thing that comes to my mind is cooperation amongst individuals to do tasks towards a set goal. Cooperation implies communication and understanding, and leadership and organization. Setting a goal implies the formulation of ideas. "Producing a civilization" implies that the ideas, tasks, and goals can't be too wacky ( have everyone dig a hole and then fill it up ) as an exercise in futility so as to not give an advantage to the group in one way or another. So I would think there has to be a certain social organization, and there could be a few, that could meet your criteria where a civilization comes about. Perhaps throw in some competition and conflict so that individuals can come up with better ideas, rather than follow around each other like zombies and re-hash the old stuff over and over again.

Next you might have to look at body structure and features. Opposable thumbs and fingers, and upright stature, are often said to have worked great for human survival, for carrying things and manipulation of objects. But would tentacles work for another life form just as well? Could there really be an octopus alien species technologically adept at sending rockets to their moon?

That is just form and function, and is complicated enough, without mentioning the necessary evolution and its steps to get to an intelligent life form.

As you said,

That's an awful lot of perfect that has to fall into place to allow for not just life, but intelligent life to form.

 

[Keln]

What is civilization? We may have ideas of what civilization is, but can we define the word universally? What really makes a civilization a civilization?

I will explain what I think defines a civilization. To me it seems there is one main difference between the civilized and uncivilized worlds. Prior to civilization, every individual was independent. That is, when we were uncivilized 'hunters and gatherers,' every person was an expert at the entire culture. Every man knew how to hunt, cook, build, make clothes and tools, etc. But when civilization arose, independence was lost and everyone became largely dependent on everyone else. The advantage of this was that individuals became more specialized. Instead of everyone being an expert in everything, some people became experts in some things and others were experts in other things. Independence was traded for specialization. This, as we can clearly see, opened up a lot of potential for development.

When I try to transcend our familiar human anecdote to define civilization universally, I come to the following general idea: Civilization is where a collection of individuals becomes dependent on each other by splitting up into groups of specialized functions. This enables more potential for growth than if each individual survived independently.
This is just my perspective on the essence of civilization, so feel free to improve on it, or to propose alternate definitions of what you are looking for.

One other example jumps out at me from this definition. Cells. Our cells have come together to form our bodies, and different groups of cells perform different functions, but all are dependent on all. (The heart couldn't live without the stomach and vice versa and etc.) So are cells considered a civilization? If not, then what is the requirement which they do not satisfy? (In other words, how do you define civilization?)

Individual cells are to the human body as individual humans are to (civilized) humanity. The more I think about this analogy, the more aspects of it I find. Look at how much more potential the human body has compared with trillions of cells which survive independently. Look at how much more potential the human species has compared with billions of humans surviving independently. It almost seems like "civilization" is a natural progression of this living world.

I really like your definition of civilization, but for the purposes of my question I am using a more basic definition, which would include cave-dwelling hunter-gatherers. I think, for the purposes of my question, I'd stick to a definition of civilization as being a species of sentient beings who have the ability to manipulate nature. The most basic form of that is creating fire, and so I use fire as a sort of "must have" for any civilization. The questions I pose aren't really focused on what kind of civilization really, just that one could emerge. I mean, once you have fire and tool use, there really is no limit to where a civilization can go. It could stay there, or it could evolve into a more technologically advanced society, with agriculture and cities. Either way, it's still a civilization compared to animals.

And, yes, I think that cells are a form of civilization. I don't think most people realize that they as an organism are actually many organisms working together. Not just the human cells, but also the many microorganisms without which we'd not be able to live. But for this discussion, I am not considering non-sentient life forms as "civilizations". I am using the term to mean the ability to use tools and make fire...or some other manipulations of nature that are analogous.

 

[Keln]

Unfortunately we only have 1 species to look at, so there's no telling.

You're most likely correct of course, but I think my real question is, what can take the place of water, and what conditions will allow for fire? I figure those two things are absolutely necessary to biology (water or an analogue) and basic civilization (fire).

 

[Drakkith]

You're most likely correct of course, but I think my real question is, what can take the place of water, and what conditions will allow for fire? I figure those two things are absolutely necessary to biology (water or an analogue) and basic civilization (fire).

Now that is a much more interesting question in my opinion. Unfortunately I haven't done much reading into this.

 

[Keln]

Here is my take on this.
Firstly, look at how fast our civilization has developed in the last 10000 years. It's insanely fast compared to the lifetime of the universe. And then look at how our technology is advancing. It's advancing at an exponential rate. In the next 10000 years, we will definitely become a multi-planetary species, provided we don't wipe ourselves out. Who knows how advanced we will be.
Assuming there is life out there, it will be either more intelligent or less intelligent than us.
In the case that is is more intelligent, using our observation of our advancement of society, wouldn't it be fair to conclude that the intelligent life is extremely intelligent and vastly more advanced than us? 10000 years is a very short span, it is very very unlikely that there is a similar species advancing at the same pace as us. Thus, if it was an extremely intelligent species will it not have probably expanded outwards and displayed observable signs of it's existence?
In the case that it is less intelligent, there are two scenarios.
1. It is simple life, which is not the focus of this discussion.
2. It is "stone age" intelligent. My argument here is the length of the stone age (3.4 million years) is only 0.0002 % of the universe's estimated lifetime. It's only a sample size of 1, but that's all we've got. If intelligent life only takes about 3.4 million years (plus minus tens of millions of years, its still tiny in comparison to the lifetime of the universe) to develop to become a highly intelligent species, there is a very low chance that intelligent life lies in the universe that has not developed into a highly intelligent species.

Just my 2 cents, feel free to refute.

You bring up some good points, and Stone Age is really all I am gunning for in my inquiry. The level of technology isn't important. The fact that any sort of "technology" can be advanced is all that matters, which is why I use fire as a requirement. That's about as basic as it gets.

I like that you brought up intelligence. There seems to be an assumption that alien species would be more intelligent, and less popular that they would be less intelligent. I am not sure that is the case. Intelligence is something that is driven purely by evolutionary pressure. Once a species reaches the intelligence level that allowed for sentience, I am not sure that evolutionary pressure really matters anymore. Consider the human race...how does natural selection even enter into the equation with our species anymore? Stupidity isn't selected for naturally anymore, nor are any other traits that have no effect on procreation. I think once a species reaches sentience, there is no longer any evolutionary pressure to make them "smarter".

Of course, I suppose if there were a planet where a lot of species were quite intelligent, it could cause a selection of higher intelligence to survive over lesser intelligence. But I am not sure it would be an order of magnitude such as the case between humans and the most intelligent animals. It's a sort of gap that once crossed no longer has any momentum to keep advancing.

 

[Evo]

Are you guys forgetting Neanderthals and Denisovans?

http://www.nature.com/news/hominin-dna-baffles-experts-1.14294

 

[Keln]

Are you guys forgetting Neanderthals and Denisovans?

http://www.nature.com/news/hominin-dna-baffles-experts-1.14294

Not forgetting them at all. It is likely, I think, that on a planet where sentient life can form there might be several competing species. It is also likely that one species would wipe out the others, and that species would be the more aggressive one.

I chuckle whenever I see people say things like "aliens would pass us by when they saw how war-like we are". Well, most likely an advanced alien race would have "won out" vs other species on their planet because they were more aggressive...more war-like. I can't even fathom a sentient race advancing without wars. Even in the animal kingdom, there is warfare of a sort. Heck, even amongst bacteria there is.

 

[Pythagorean]

Nanderthals and Denisovans are humans, too, so I assumed they were included in the discussion.

 

[Evo]

Neanderthals and Denisovans are humans, too, so I assumed they were included in the discussion.

They're not homo sapiens. If they hadn't died out as a separate species or sub species, scientists can't seem to decide which, we would have different human-like intelligent groups.

From the article I posted.

 

[Pythagorean]

Not human-like, human!

We (Homo Sapiens) actually mated with Neanderthals (I think Denisovans too) and the resulting descendants of that are still alive today.

 

[Evo]

Not human-like, human!

We (Homo Sapiens) actually mated with Neanderthals (I think Denisovans too) and the resulting descendants of that are still alive today.

Where are you reading that they are humans like us? They have differences. Like I said in a previous posts, scientists are going back and forth between same species/sub-species.

Were Neanderthals a sub-species of modern humans? New research says no
Nov 18, 2014

In an extensive, multi-institution study led by SUNY Downstate Medical Center, researchers have identified new evidence supporting the growing belief that Neanderthals were a distinct species separate from modern humans (Homo sapiens), and not a subspecies of modern humans.

Read more at: http://phys.org/news/2014-11-neanderthals-sub-species-modern-humans.html#jCp

Here is a bit more, there is a ton of work of course, too much for a thread.

The most recently announced research suggests that humans and neanderthals were right on the edge of being different species, and their offspring may have been of low fertility - similar to what happens when donkeys and horses breed, but to a lesser degree. This conclusion is based on the lack of neanderthal genes on modern human X and Y chromosomes.

Here is a quote:
"The team showed that the areas with reduced Neanderthal ancestry tend to cluster in two parts of our genomes: genes that are most active in the male germline (the testes) and genes on the X chromosome. This pattern has been linked in many animals to a phenomenon known as hybrid infertility, where the offspring of a male from one subspecies and a female from another have low or no fertility.

'This suggests that when ancient humans met and mixed with Neanderthals, the two species were at the edge of biological incompatibility,' said Reich, who is also a senior associate member of the Broad Institute and an investigator at the Howard Hughes Medical Institute. Present-day human populations, which can be separated from one another by as much as 100,000 years (such as West Africans and Europeans), are fully compatible with no evidence of increased male infertility. In contrast, ancient human and Neanderthal populations apparently faced interbreeding challenges after 500,000 years of evolutionary separation."

http://www.sciencedaily.com/releases/2014/01/140129134956.htm.

 

[Pythagorean]

The scientific article cited by your source:

Neanderthals are one of the most intensely studied groups of extinct humans, as aspects of their phylogeny and functional morphology remain controversial.

http://onlinelibrary.wiley.com/doi/10.1002/ar.23040/full

Are you sure you're not confusing "modern human" with "human"?

Here's the article I read on mating:
http://www.nature.com/news/modern-human-genomes-reveal-our-inner-neanderthal-1.14615

 

[Evo]

The scientific article cited by your source:
http://onlinelibrary.wiley.com/doi/10.1002/ar.23040/full

Are you sure you're not confusing "modern human" with "human"?

Here's the article I read on mating:
http://www.nature.com/news/modern-human-genomes-reveal-our-inner-neanderthal-1.14615

Yes, there is some neanderthal dna in some humans, but that doesn't mean that they were completely the same. That's an area of contention right now. I read the studies back and forth and I certainly cannot say who is right. My point being that it is possible that more than one branch, sub-species, what-ever, were able to develop some level of intelligence separately, it wasn't just modern day humans.

Over the past 15 years, Svante Pääbo, a geneticist at the Max Planck Institute of Evolutionary Anthropology, and his colleagues have uncovered an entirely new source of evidence about the nature of Neanderthals: their DNA. Starting with those fossils from the Neander Valley, they extracted bits of genetic material that had survived tens of thousands of years. Eventually, they were able to assemble the fragments into the entire Neanderthal genome.

It's clearly different from the genome of any human alive today, sprinkled with many distinctive mutations. These mutations accumulated in a clock-like way, and by tallying them up, Pääbo and his colleagues estimate that Neanderthals and humans share a common ancestor that lived 800,000 years ago. It's possible that the ancestors of Neanderthals expanded out of Africa then, while our own ancestors stayed behind.

http://www.pbs.org/wgbh/nova/evolution/are-neanderthals-human.html

 

[Keln]

For the purposes of this discussion, I suppose both Neanderthals and Denisovans count. Both had tool use and possibly fire. So, that meets the criteria I set forth.

 

[Pythagorean]

Yes, there is some neanderthal dna in some humans, but that doesn't mean that they were completely the same. That's an area of contention right now. I read the studies back and forth and I certainly cannot say who is right. My point being that it is possible that more than one branch, sub-species, what-ever, were able to develop some level of intelligence separately, it wasn't just modern day humans.

They weren't completely the same (I never argued that). They all belong to the same clade sprouting from H. erectus (i.e. humans) but they didn't develop intelligence separately. The intelligence was already there, from our common ancestor (H. erectus). They were definitely using tools, and there's evidence of fire usage too!

 

[Evo]

Yes, Homo Erectus had fire and tools, and it's thought that even earlier species such as homo habilis and homo rudolfensis may also have used fire and had simple tools, but they are all different species, the genus is homo, but there are different species. So, I agree with you. I was posting in response to a comment that we only have one species with intelligence to look at on earth. I'm way too literal.

Evolutionary Relationships

The earliest Homo erectus were contemporaries of the late Homo habilis in East Africa for several hundred thousand years. This suggests that the immediate ancestor of Homo erectus was an early Homo habilis or possibly another yet to be discovered species of early humans. Homo erectus was a very successful human species, lasting at least 1.5 million years, though their numbers apparently remained relatively low. Some of them eventually evolved into our species, Homo sapiens

. That evolutionary transition was well under way by 400,000 years ago but was not complete until 200,000-100,000 years ago andpossibly even later in some regions.

http://anthro.palomar.edu/homo/homo_2.htm

 

[zoobyshoe]

Yes, Homo Erectus had fire and tools, and it's thought that even earlier species such as homo habilis and homo rudolfensis may also have used fire and had simple tools, but they are all different species, the genus is homo, but there are different species. So, I agree with you.

Every time Pyth supports his statement that Neanderthals and Denisovians are human you seem to shrink away from confirming that out of some inexplicable fear some non-specified element of the thread's readership will misunderstand that to mean they were exactly like us, and you keep emphasizing the differences. Has there been some past chronic problem with people thinking Neanderthal = Homo Sapiens?

 

[Evo]

Every time Pyth supports his statement that Neanderthals and Denisovians are human you seem to shrink away from confirming that out of some inexplicable fear some non-specified element of the thread's readership will misunderstand that to mean they were exactly like us, and you keep emphasizing the differences. Has there been some past chronic problem with people thinking Neanderthal = Homo Sapiens?

No, as I explained, I was responding to an earlier to post that Earth only has one species that developed intelligence, that's incorrect, that's all. Neaderthals are believed to be a different species than modern humans, but like I also said, some scientists think they might. How many times do I have to keep repeating this?

Some of the genes, meanwhile, appear to have led to fertility problems. For instance, Sankararaman found that the X chromosome is almost devoid of Neanderthal DNA. This suggests that most Neanderthal DNA that wound up on the X chromosome made the bearer less fertile – a common occurrence when related but distinct species interbreed – and so it quickly disappeared from the human gene pool. "Neanderthal alleles were swept away," says Sankararaman.

"This underlines that modern humans and Neanderthals are indeed different species," says http://www.eva.mpg.de/evolution/staff/spoor/ of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was not involved in any of the studies.

http://www.newscientist.com/article...light-skins-and-infertility.html#.VOonr3zF9JZ

 

[zoobyshoe]

No, as I explained, I was responding to an earlier to post that Earth only has one species that developed intelligence, that's incorrect, that's all.

Ah, I get it! You mean this:

Unfortunately we only have 1 species to look at, so there's no telling.

 

[Evo]

Ah, I get it! You mean this:

Yes, I now owe you a shrubbery.

 

[Pythagorean]

Right. I see where Evo is coming from. It's similar to wolves and dogs; both canines, but distinct species (that can interbreed) which challenges a rigid notion of "species" in the first place, since interbreeding is part of the definition of species.