Why Didn't Dinosaurs Evolve Into Intelligent Beings?

[Vrbic]

Hi, I'm not a biologist and I'm not studying biology. But I'm curious so I read and watch some popular papers or videos. I have a question but first of all, I would like to conclude what I think is true:

a) The evolution is a process of adapting of living to live in some environment.

b) The evolution causes the pressure of the environs.

c) Dinosaurs didn't develop into intelligent creatures, because they were dominant (some were big, some were quick,...) in their environment. There wasn't any significant ambient pressure for that.

Questions:

1) Dinosaurs existed around 130 million years, i.e., enough time to the evolution. Why didn't any smaller dinosaur or not dominant animal developed into the intelligent being?

2) What caused the human developed into an intelligent being?

Please, let me know if the statements are alright (at least roughly) and answer if possible. Speculations or hypotheses are also welcome.
Thank you all.

 

[russ_watters]

You are largely correct in your understanding. To restate, the thing to understand is that other than complexity, evolution does not have a specific "direction". Intelligence is nor a goal or an inevitable outcome. Organisms need to eat and avoid being eaten long enough to reproduce and that is pretty much it.

If anything, success and stasis stunts evolution, so the longevity of the dinosaurs is evidence against radical evolutionary pressure. So this is the right question:

Why didn't any smaller dinosaur or not dominant animal developed into the intelligent being?

I'm not sure if there is a good answer. Maybe they were being eaten too fast for behavioral complexity to help much.

 

[pinball1970]

Hi, I'm not a biologist and I'm not studying biology. But I'm curious so I read and watch some popular papers or videos. I have a question but first of all, I would like to conclude what I think is true:
a) The evolution is a process of adapting of living to live in some environment.
b) The evolution causes the pressure of the environs.
c) Dinosaurs didn't develop into intelligent creatures, because they were dominant (some were big, some were quick,...) in their environment. There wasn't any significant ambient pressure for that.
Questions:
1) Dinosaurs existed around 130 million years, i.e., enough time to the evolution. Why didn't any smaller dinosaur or not dominant animal developed into the intelligent being?
2) What caused the human developed into an intelligent being?

Please, let me know if the statements are alright (at least roughly) and answer if possible. Speculations or hypotheses are also welcome.
Thank you all.

Evolution is a filter system it does not "cause" environs or the environment. The environment influences evolution not the other way round. Climate change is a good example, as the planet heats up certain animals will take advantage of this increase in temperature and others may struggle and die off.

Why did humans become intelligent is a million dollar question, plenty of good ideas with evidence to support them (we are not encouraged to speculate, way too much science out there to learn before we have to do that!)

https://en.wikipedia.org/wiki/Evolution_of_human_intelligence

I would read a good book on the mechanisms and evidence for evolution, "Why evolution is true" is a great book, Jerry Coyne.

 

[berkeman]

Speculations or hypotheses are also welcome.

We try to avoid those here at the PF.

BTW, have you read through the thread that is stickied at the top of the Biology forum (this forum where we are) about Evolution?

https://www.physicsforums.com/threads/learn-about-evolution-evolution-introduction.543950/

It is a good introduction, and has links to more information.

 

[BillTre]

b) The evolution causes the pressure of the environs.

If by "causes the pressure of the environs", you mean effecting in some manner, changes in the environment;
Then, the relationship between evolving organisms and the environment to a two way thing.

There are clear cases of biology having big influences on the environment.
One of the largest effects is the oxygenation of the atmosphere.
First there was no oxygen, then biology started producing oxygen.
Iron in the oceans oxidized and fell out of solution in the oceans (big effect).
Further oxygenation eventually increased atmospheric oxygen levels. It also affected weathering of rocks.

As a result of an oxygenated atmosphere, the biological environment was changed.
This oxygenated atmosphere had effects on the biological entities in many environments (going in environment to biology now).
Most anaerobes did not do well in an oxygenated environment and had to find (in a non-anthropomorphic way) oxygen lacking refuges in which to live.
Aerobic organisms evolved to take advantage of the increased oxygen availability in the new environment.

c) Dinosaurs didn't develop into intelligent creatures, because they were dominant (some were big, some were quick,...) in their environment. There wasn't any significant ambient pressure for that.

I don't buy the part in red. Here is way:
Being dominant (to me, in the context of evolution) means being successful in the evolutionary processes (survival and reproduction of individuals, persistence of species, and in evolving of new species from pre-existing ones (this would be speciation)).
Largeness might be an evolutionary trap, more difficult to get out of.
Important to any argument about dinosaurs, is that they evolved many species with lots variations on their body plans.
Their dominance was not necessarily a hindrance to evolving intelligence.
however, the lacking of "significant ambient pressure" might reduce or eliminate any selection for higher intelligence.
Lacking other things and conditions that would be required to evolve intelligence has also been argued (see below).

If being dominant is being large, then the arguments might be different.

Why didn't any smaller dinosaur or not dominant animal developed into the intelligent being?

Although there were small dinosaurs, they would have had the same problem generally as any others which could easily have been the same as above:

the lacking of "significant ambient pressure" might reduce or eliminate any selection for higher intelligence.

There were also small mammals around with the dinosaurs. They eventually evolved into people with intelligence. However, it took millions of years of evolutionary set-up time to generate the animals that eventually evolved into people. At the time of the dinosaurs, presumably, they also lacked

"significant ambient pressure" might reduce or eliminate any selection for higher intelligence.

Lacking of other biological parts and/or conditions that might be required to evolve intelligence can also be argued.

The required parts/conditions class of explanations which involve arguments about how the dinosaurs might be lacking one or more critical traits, preventing them from being able to put together all the biological parts to achieve intelligence.
These might include:

• brain size
• brain structure
• developmental processes underlying brain/body structures
• an intellectually challenging environment (living in trees (complex 3-D environment) prior to evolving humans) that might favor increased computational abilities.
  
• environmental changes (such as forests --> grasslands) where intelligence could be useful because it can change faster than biology evolves (and therefore adaptive).

This is a more theoretical and conjectural view.

2) What caused the human developed into an intelligent being?

Controversial, with no common conclusion at this time.
Many possible factors.

To restate, the thing to understand is that other than complexity, evolution does not have a specific "direction".

Things are more complex than this.

There are certainly many highly complex organisms.
And evolution certainly increased complexity from its low complexity beginnings when the non-living whatever-they-were's that life evolved from (going from a non-self-sustaining level of complexity to the (presumably) much higher levels of complexity found in today's self-sustaining biological organisms).

However, there are many well known examples of evolution going in the direction of reduced complexity. Therefore the general statement is wrong.
Wikipedia biol complexity article here.

Parasites provide many common examples of structurally simplified organisms (although they may evolve more elaborate life cycles).
From a wikipedia article on parasites:

Trait loss
Parasites can exploit their hosts to carry out a number of functions that they would otherwise have to carry out for themselves. Parasites which lose those functions then have a selective advantage, as they can divert resources to reproduction. Many insect ectoparasites including bedbugs, batbugs, lice and fleas have lost their ability to fly, relying instead on their hosts for transport.[88] Trait loss more generally is widespread among parasites.[89]

This can even go as far as Giardia, which is a eukaryotic intestinal parasite that has lost its mitochondrial function.

Mitochondria themselves are examples of complexity reductions in evolution. But perhaps not depending on point of view (how analyzed).
The standard story would be something like:
A bacteria takes up residence inside of an archaeal cell (similar to bacterial cells in many ways),
The bacteria evolves into the mitochondria. Its get what it needs from its host archaeal cell and gives back ATP,
The mitochondria's genome has thrown away almost all of a typical bacteria's genes.
Going from the 1,500 to 2,000 genes in many bacteria, mitochondria have:

The number of mitochondrial protein genes varies from 3 to 67, while tRNA gene content varies from 0 to 27.

according to this article.

This is the "higher" and more complex eukaryotic cell.
It can be seen as both a complexity decrease (individual mitochondria) and as an increase (from a bacteria and archaeal cell to a eukaryotic cell).
The archeal cell has formed a much enlarged eukaryotic cell body (based on energy from the mitochondria), has a relatively huge genome that encodes to production of many different highly specialized proteins and larger structures.
A eukaryotic cell can contain hundreds or thousands of individual mitochondria (each with a tiny little genome).
There is complex decision to be made on how balance the complexities of the mitochondrial (and the many copies of the mitochondria/cell) and the eukaryotic cell of which it is a significant part, if you want to consider the problem from that point of view.

Another way to consider evolution might be the changes in ecosystems (a different kind of biological entity) over time.
Ecosystems are more complex than when there were none (pre-biology).
There are a lot of complex ecosystems.
However, ecosystems can also go in a path toward reduced complexity.
Changing climatic conditions (no rainfall? desertification), invasive species (Caulerpa in the Mediterranean), or loss of a top predator can result in an ecosystem "reduction" (usually thought of as number of species; sometimes as capture, by the biology, of energy going through the environment).

 

[berkeman]

Great post @BillTre thanks.

Most anaerobes did not do well in an oxygenated environment and had to find (in a non-anthropomorphic way) oxygen lacking refuges in which to live.

LOL. Never anthropomorphize anaerobes. (you know the rest of that joke)

 

[BillTre]

Never anthropomorphize anaerobes.

Don't want to be confusing people!

 

[russ_watters]

I
Things are more complex than this.

There are certainly many highly complex organisms.
And evolution certainly increased complexity from its low complexity beginnings when the non-living whatever-they-were's that life evolved from (going from a non-self-sustaining level of complexity to the (presumably) much higher levels of complexity found in today's self-sustaining biological organisms).

However, there are many well known examples of evolution going in the direction of reduced complexity. Therefore the general statement is wrong.
Wikipedia biol complexity article here.

Yeah, I thought I might get some pushback on that and couldn't think of a way to mitigate it. Perhaps just saying time elapsing (not evolution itself) enables complexity would be enough. The point being that changes happen over time and can - but don't necessarily linearly - build up over time. But of course, evolution can select changes out.

I'm wondering if there is a way to (or if it has been) quantify/measure/model complexity. It would seem to me that it should follow a random walk type idea. They should happen at a certain average rate, but then evolution should start selecting them out at some time, leading to a reduction of the rate of increase.

 

[BillTre]

I'm wondering if there is a way to (or if it has been) quantify/measure/model complexity. It would seem to me that it should follow a random walk type idea. They should happen at a certain average rate, but then evolution should start selecting them out at some time, leading to a reduction of the rate of increase.

I read an article or a chapter by Stephen J Gould, basically making that argument, but realizing it started from zero (with the initiation of biology), and then increased randomly (but constrained not to go to 0). It looks like progress, but it isn't always.

From SJ Gould wikipage:

Gould favored the argument that evolution has no inherent drive towards long-term "progress". Uncritical commentaries often portray evolution as a ladder of progress, leading towards bigger, faster, and smarter organisms, the assumption being that evolution is somehow driving organisms to get more complex and ultimately more like humankind. Gould argued that evolution's drive was not towards complexity, but towards diversification. Because life is constrained to begin with a simple starting point (like bacteria), any diversity resulting from this start, by random walk, will have a skewed distribution and therefore be perceived to move in the direction of higher complexity. But life, Gould argued, can also easily adapt towards simplification, as is often the case with parasites.[58]

I think he also wrote a book on this.

 

[Laroxe]

I think its better to think of evolution in terms of fitness rather than an environmental adaptation, humans have managed to populate a huge range of different environments. Its a common idea that in evolutionary terms intelligence is an obvious advantage, but we are a bit biased in this belief. From the 15+ members of the homo genus, all presumably intelligent we are the only survivors and we haven't been around long and many of our nearest living relatives are endangered. In biological terms intelligence is also very costly, our large brain complicates birth, increasing early mortality and it uses around 20% of our energy reserves. It has been suggested that humans might be to intelligent for their own good, our technology representing an existential threat. There is also some evidence that among the most intelligent humans fitness is reduced.
https://www.scientificamerican.com/article/bad-news-for-the-highly-intelligent/

 

[Vrbic]

If by "causes the pressure of the environs", you mean effecting in some manner, changes in the environment;
Then, the relationship between evolving organisms and the environment to a two way thing.
.
.
.

Thank you very much for the inspiration and comprehensive response.

 

[cosmik debris]

I think its better to think of evolution in terms of fitness rather than an environmental adaptation, humans have managed to populate a huge range of different environments. Its a common idea that in evolutionary terms intelligence is an obvious advantage, but we are a bit biased in this belief.

In terms of adaptation intelligence would appear to allow faster adaptation than genes. If an intelligent creature is in a cold climate they might invent clothing rather than wait several generations for their fur to grow.

Cheers

 

[trainman2001]

We're also finding out, much to some people's chagrin, that we're not the only intelligent life form on Earth. Octopus, Honey Bees, Birds, Orca, Bottle-nosed Dophins, all have more innate intelligence than previously thought. Bird brains have 10X more neurons packed into their small spaces leading to recent understanding that song birds, crows, parrots, have mental capacity approaching Chimps. Humans are a special case probably related to our ability to manipulate objects. Octopus are handicapped by short life spans. Birds don't have hands, although watching a parrot eat a peanut shows how dexterous they are with their feet. The discovery of neuron packing in bird brains is a very recent discovery when some scientists decided to do some serious micrographic studies of the brain physiology and found that their brains were structured entirely different than mammalian brains. Now this poses an interesting thought. We know that birds descended from some dinosaurs, what if those dinosaurs' brains also had the neuron packing found in modern birds? Would they not have been more "intelligent" than we have believed? Small brains doesn't necessarily mean low intellect.

 

[AlexCaledin]

- to me, adaptation advantages hardly ever matter practically - because the whole process remains incredibly improbable anyway. It's, just as well, quite enough to imagine that the cosmic rays, from the whole universe, did all the tricks, making the first live cell and all the subsequent genetic reprogramming.

 

[Buzz Bloom]

There is also some evidence that among the most intelligent humans fitness is reduced.

Hi Laroxe:

Thanks for the citation of the SA article. It was interesting to read, but I found the description of the research seemed to me to show that the researchers ignored some likely relevant aspects of the topic. Here are two examples:
1. Some disorders (e.g., Asperger's syndrome) have a correlation with a higher than typical degree of problem solving skills. This might be that in this case, the disorder is the cause of higher IQ rather than the other way around.
2. Higher IQ parents tend to produce children with higher IQ children than those of lower IQ parents. Some of these higher IQ parents put more pressure on their children to get high grades in school than do lower IQ. parents. The higher pressure may well cause some of the psychological issues of higher IQ children found in the reported research.

Regards,
Buzz

 

[pinball1970]

- to me, adaptation advantages hardly ever matter practically - because the whole process remains incredibly improbable anyway. It's, just as well, quite enough to imagine that the cosmic rays, from the whole universe, did all the tricks, making the first live cell and all the subsequent genetic reprogramming.

Adaptation advantages mean that organism has a better chance of surviving to reproduce.

What do you mean "incredibly improbable?" Evolution?

 

[jim mcnamara]

Let's not wade into the IQ swamp, please. IQ is simply a problem solving test that helps to predict academic success. Since this is not a Psychology forum, please do not get into speculation about IQ and Natural Selection. Counterexample: An octopus can solve problems, too. But would not fare well taking a Stanford-Binet or Wechsler IQ test. A ridiculous comparison, as you can see. Because it is very likely we do not fully understand all of the dimensions and manifestations of intelligence measurement across species.

Octopus, Popular science article from SA: https://www.scientificamerican.com/article/are-octopuses-smart/

Note the timeline for the IQ test that became a de facto standard for a long time:
https://en.wikipedia.org/wiki/Stanford–Binet_Intelligence_Scales

E. O. Wilson argues that hypersocial, hypercooperative human behavior with very complex verbal communications was selected for. See the 'Social Conquest of Earth'

 

[trainman2001]

And of course the whole process is entirely random, or at least it appears so. Living things don't consciously alter their DNA to make new subsets or species. The mutations simply happen and the particular mutation that invokes an advantage (for procreation) will be carried on as a possible change. It's just we're talking about vast permutations. Slight mutations from generation to generation create vast differences. Just in humans say, current forms are around for 100,000 years could have 600,000 generations and that's already after we we're bipedal, had opposed thumbs, were out of the tress, etc. And it's probably many more generations than that. Nature has had a billion or more generations to figure out how make a good eye (ball, lens, iris, retina) which is why ours and squids are so closely analogous. When you've got a billion generations to screw around with permutations you can get some pretty interesting things.

 

[jim mcnamara]

@AlexCaledin

In terms of adaptation intelligence would appear to allow faster adaptation than genes. If an intelligent creature is in a cold climate they might invent clothing rather than wait several generations for their fur to grow.

Natural Selection does not work like that. Period. It does not and cannot have "goals in mind" because it is a random process of differential survival. Randomness is the change in genetic makeup.
In your example, if they really needed fur to survive they would all die. Plus humans have been wearing clothing or some outer covering for a very long time, back more than 83000ya. In Africa apparently.

What this study did: use clothing louse divergence from head louse DNA as a proxy for when humans started wearing clothing.

Origin of Clothing Lice Indicates Early Clothing Use by Anatomically Modern Humans in Africa
Melissa A. Toups Andrew Kitchen Jessica E. Light David L. Reed

Molecular Biology and Evolution, Volume 28, Issue 1, 1 January 2011, Pages 29–32,
https://doi.org/10.1093/molbev/msq234

Abstract:

Clothing use is an important modern behavior that contributed to the successful expansion of humans into higher latitudes and cold climates. Previous research suggests that clothing use originated anywhere between 40,000 and 3 Ma, though there is little direct archaeological, fossil, or genetic evidence to support more specific estimates. Since clothing lice evolved from head louse ancestors once humans adopted clothing, dating the emergence of clothing lice may provide more specific estimates of the origin of clothing use. Here, we use a Bayesian coalescent modeling approach to estimate that clothing lice diverged from head louse ancestors at least by 83,000 and possibly as early as 170,000 years ago. Our analysis suggests that the use of clothing likely originated with anatomically modern humans in Africa and reinforces a broad trend of modern human developments in Africa during the Middle to Late Pleistocene.

 

[pinball1970]

And of course the whole process is entirely random

Mutations are random, the filter, natural selection is the opposite of random.

 

[trainman2001]

Well… it's not really by plan… those mutations that produce positive results go forward, those that don't are extinguished or if they're benign and don't make much difference, they would continue also. If it affects the ability to feed, fight disease, and procreate positively, then it goes on. It's actually pretty random, since it's happenstance if the mutation happens to occur in a situation where it works. Change the environs and that same mutation might have the opposite effect.

 

[Hernik]

Hi there! Great questions. If you're interested in why humans became "intelligent" you might want to read this study which recently appeared in Nature.

https://natureecoevocommunity.natur...uman-brain-from-ecology-and-seemingly-culture

The conclusion is that humans got bigger brains (which is easier to quantify than intelligence) from a history of cooperation (Edit: and culture in the sense of being able to learn from each other). Lately Homo sapiens (that's you and me) seem to have lost some brain power (compared to ie neanderthals) after we developed an appetite for competing with other groups of humans. (There you go - we got dumber but learned to appreciate football!) It is a computer model and debated. But an interesting approach to how humans got the brains we have.

One thing which is important to understand about evolution is, that it is completely blind. No purpose. No goal. It is a mechanism like the sieve in the sandbox - some grains go through and some don't. The environment (in a broad sense - nature, in-species-competition, availability of food, sexual partners, changes in climate, changes in amounts of and types of predators, new diseases ...) is the sieve and some individual organisms cope better with the challenges and have more offspring that survive. Nobody is trying to reach a goal. All organisms just live, and do what they think is right and feel good with, and some just make it marginally better in life because of inherited abilities. If a trait becomes important in that process it will be amplified quickly in very few generations. And we who live today are simply the offspring of those that made it a little better than the others in former generations.

Also - evolution happens all the time. We are changing all the time. Even if a species seems to be exactly the same through millions of years, it is evolution that keeps it the same. If the environment changes the species change. If there is no significant changes in the environment then the species keep changing into what it already is.. does that make sense?

Biologists might want to correct this post as I am just a layman who used to ask the same questions you do. Please do.

 

[Buzz Bloom]

If there is no significant changes in the environment then the species keep changing into what it already is.. does that make sense?

Hi Hernik:

It does not make sense to me because it overlooks that change continues whether the environment changes or not. Over a long period of time new characteristics will enter the population's total genome which are just as good for production as what was in the genome before. Therefore the population will be come more diverse in its characteristics.

If some environmental change separates a population into two groups that after a long while can no longer interbreed even if the physical barrier goes away, then these two separate groups will be two distinct species.

Regards,
Buzz

 

[Hernik]

Hi Hernik:

It does not make sense to me because it overlooks that change continues whether the environment changes or not. Over a long period of time new characteristics will enter the population's total genome which are just as good for production as what was in the genome before. Therefore the population will be come more diverse in its characteristics.

If some environmental change separates a population into two groups that after a long while can no longer interbreed even if the physical barrier goes away, then these two separate groups will be two distinct species.

Regards,
Buzz

Hi Buzz. I totally agree. What I am trying to say is that evolution is going on even through no change might be apparent from generation to generation (say frogs or crocodiles). It is something that used to confuse me into thinking that evolution is something that happens when necessary. On the contrary - as you point out - it is going on all the time to an extend where species separated geographically become two after some time simply because the changes in the two groups become too large.

 

[alantheastronomer]

b) The evolution causes the pressure of the environs.

I think you must mean: The evolution is caused by the pressure of the environs.

1) Dinosaurs existed around 130 million years, i.e., enough time to evolve. Why didn't any (of them) develop into intelligent beings?

Well, dinosaurs were cold-blooded, which inhibited their brains' ability to develop no matter how much time has passed.

2) What caused humans to develop into intelligent beings?

The one factor that seems to enable human intelligence to develop is brain size. In order for that to occur, several musculoskeletal adaptations had to evolve: First, walking upright; Second, in order for there to be enough room in the cranium for a larger brain to develop, a recessed jaw. This is something I saw on an episode of NOVA on PBS.

 

[pinball1970]

Well… it's not really by plan… those mutations that produce positive results go forward, those that don't are extinguished or if they're benign and don't make much difference, they would continue also. If it affects the ability to feed, fight disease, and procreate positively, then it goes on. It's actually pretty random, since it's happenstance if the mutation happens to occur in a situation where it works. Change the environs and that same mutation might have the opposite effect.

I did not infer there was a plan I said natural selection is the opposite of random. A chick that is born slightly smaller body weight slightly weaker than its siblings is less likely to compete for food and may die as a result. This is zero to do with random mutations, this is variation within a species and natural selection playing out . A random mutation that is beneficial is rare as you pointed out, but the filter natural selection, still operates on that gene and this is a non-random process.

 

[Rive]

I did not infer there was a plan I said natural selection is the opposite of random.

There is some randomness involved in this too. You need a population (and also: adequate number of individuals with the mutated gene within the population) large enough for statistics to kick in.

 

[cosmik debris]

Well, dinosaurs were cold-blooded,

Are you sure?

https://www.nature.com/news/dinosaurs-neither-warm-blooded-nor-cold-blooded-1.15399

Cheers

 

[pinball1970]

There is some randomness involved in this too. You need a population (and also: adequate number of individuals with the mutated gene within the population) large enough for statistics to kick in.

I was addressing the statement "the process is mostly random." I appreciate the randomness of events, pregnancy death meal starvation disease lightning strike etc within populations. One can still make some decent predictions on populations in terms of gene frequencies a;; else being equal, Hardy Weinberg springs to mind.The word "randomness" in the same sentence as evolution usually implies a misconception.

 

[Buzz Bloom]

The word "randomness" in the same sentence as evolution usually implies a misconception.

Hi pinball:

I confess this confuses me. I tried to locate in this thread (with a quick search) an instance of "randomness" and "evolution" in the same sentence so I could evaluate whether there was also a misconception. Unfortunately, I failed to find it. I also tried to find "the process is mostly random", and I could not find that either. Would you please post the post numbers where you found these texts?

Regards,
Buzz

 

[Rive]

The word "randomness" in the same sentence as evolution usually implies a misconception.

In the same time, forgetting about the randomness involved is a bit dangerous given the situation of some species with decreased population.

 

[BillTre]

Randomness and evolution, as already mentioned, are intertwined in a few different ways.

One is that mutations are often considered to happen randomly.
Usually they do, but not always:

• rates of mutations can be increased in times when an organism is stressed, but not as much as was previously thought
  
• in some specific cases, the occurrence of particular mutations can be increased in probability (antibody gene recombination, mutation within a single organism's cells; yeast mating type locus, changes by directed movement of DNA sequences to determine which mating type a yeast cells is)

Both are based upon mechanisms that have most likely been selected for because they yield better survival.

Selection vs. Random Drift:
Selection (natural or human driven) can impose a non-random direction to changes.
The always present alternative to selection is change that happens randomly.
This can be due to the lack of strong selective values (usually at a molecular level) of one allele vs. another.

Another way random changes can have more impact on a population depends on the size of the population in question.

forgetting about the randomness involved is a bit dangerous given the situation of some species with decreased population.

As an evolving population's size goes down it becomes more likely to change randomly and the rate of adaptive change in a population's gene frequencies is decreased for a number of reasons. A large population reduces the likelihood that a population's gene frequencies will change randomly and increases the strength of natural selection on population.
Extreme examples:
Small population: The gene changes in an inbred population of mice being maintained through brother sister crosses. This is explained by the random inheritance of the same allele of a particular gene by a limited number of offspring.
Large population: a global population of interbreeding bacteria.

 

[pinball1970]

Hi pinball:

I confess this confuses me. I tried to locate in this thread (with a quick search) an instance of "randomness" and "evolution" in the same sentence so I could evaluate whether there was also a misconception. Unfortunately, I failed to find it. I also tried to find "the process is mostly random", and I could not find that either. Would you please post the post numbers where you found these texts?

Regards,
Buzz

Don't be confused the words are not there I just looked back myself
The subject was evolution and the phrase included "random/mostly random" which I thought was not a great way to describe it.
Bill has pointed out that random can be used describing evolution and he used random/ly/ness ten times in all in the last post and all perfectly valid.

 

[lavinia]

We try to avoid those here at the PF.

BTW, have you read through the thread that is stickied at the top of the Biology forum (this forum where we are) about Evolution?

https://www.physicsforums.com/threads/learn-about-evolution-evolution-introduction.543950/

It is a good introduction, and has links to more information.

Much of this thread is speculation and often discussions of Evolution are speculative. You might demand scientific discussions of technical questions rather than broad discussions of such things as how humans became intelligent. Or maybe reroute this thread to General Discussion.

 

[jim mcnamara]

@lavinia is correct. Posts here need to move off of waffly topics or moved to general discussion.

So, Moved to GD.