Is evolution still possible on a large scale?

[Jaysyn]

In a strict Darwinian sense I would say no when it comes to humans. Of course, humans are not the only species on the planet - much to the chagrin of the religious fanatics - and evolution continues among isolated populations much as it always has as Dawkins showed in his latest book.

Humans are not really "isolated" and human culture interferes with reproduction and survival anyway.

Humans as a whole have become significantly taller on average since the 1700-1800's. Wouldn't this be a result of large scale evolution? No pun intended.

[Anomalocaris]

In a strict Darwinian sense I would say no when it comes to humans. Of course, humans are not the only species on the planet - much to the chagrin of the religious fanatics - and evolution continues among isolated populations much as it always has as Dawkins showed in his latest book.

Humans are not really "isolated" and human culture interferes with reproduction and survival anyway.

Humans as a whole have become significantly taller on average since the 1700-1800's. Wouldn't this be a result of large scale evolution? No pun intended.

No, not any more than the fact that Americans have become fatter over the last 100 years represent any sort of evolutionary change. Evolutionary change has to be genetic and heritable, not just a biological reflex to environmental changes such as diet and nutrition that would go away if the change is reversed.

[Jaysyn]

No, not any more than the fact that Americans have become fatter over the last 100 years represent any sort of evolutionary change. Evolutionary change has to be genetic and heritable, not just a biological reflex to environmental changes such as diet and nutrition that would go away if the change is reversed.

But we know there are genes that control height. Sure, height has environmental factors, but so does surviving to reproduce in the first place.

[Anomalocaris]

Genes predispose a person to be taller or shorter relative to his peers. 300 years ago certain proportion of people had the tall gene, and certain proportion had the short gene. As nutrition got better and other environmental factors promoted healthy growth, people with the tall genes remained taller relative to people with short gene. But people with both the tall and short gene are now taller than their ancestors, so the average height went up.

Whether or not any genetic evolution occurred in that process depends on whether the proportion of people in the population with the short gene also decline during the same period to contribute to the increase in average height. If so, the evolution has taken place. Short gene is being selected out of existence.

If not, and changes in height is caused by increase in average height without changes in the proportion of people with the tall and short gene, then no evolution has taken place, only response to environment. In this case, Even though genes contribute to relative height of an individual within the population, it had no role in the increase of average height.

[Minimalist]

In a strict Darwinian sense I would say no when it comes to humans. Of course, humans are not the only species on the planet - much to the chagrin of the religious fanatics - and evolution continues among isolated populations much as it always has as Dawkins showed in his latest book.

Humans are not really "isolated" and human culture interferes with reproduction and survival anyway.

Humans as a whole have become significantly taller on average since the 1700-1800's. Wouldn't this be a result of large scale evolution? No pun intended.

No, not any more than the fact that Americans have become fatter over the last 100 years represent any sort of evolutionary change. Evolutionary change has to be genetic and heritable, not just a biological reflex to environmental changes such as diet and nutrition that would go away if the change is reversed.

That's a good analogy, Chuck.

[downbeatplumb]

Humans are changing the environment to suit themselves on a massive scale and in ,as far as I know, a unique way. Some animals can change one part of their environment, I'm thinking of beavers making dams here, but humans can change everthing and can even live in space.

So will evolution happen yes, but in gradual drift, until such time as there is an unusual spur to evolution, occupying another planet, a devastating virus or meteorite strike.

[Anomalocaris]

Humans are changing the environment to suit themselves on a massive scale and in ,as far as I know, a unique way. Some animals can change one part of their environment, I'm thinking of beavers making dams here, but humans can change everthing and can even live in space.

So will evolution happen yes, but in gradual drift, until such time as there is an unusual spur to evolution, occupying another planet, a devastating virus or meteorite strike.

Human impact on the environment is not large when compared to some organisms like Cyanobacteria. Without Cyanobacteria there would be no oxygen in the atmosphere, no iron ore or fossil fuel in the ground, metabolism efficient enough to support complex life would be impossible. Earth would have an atmosphere like the saturn moon Titan, and there would no life on it's surface large enough for human eye to see.

Dying because genetic weakness that makes one unable to cope in a darwinian manner with some environmental changes is not the only selection pressure that is making humans evolve. Human society impose extremely strong selective pressures based on social economic behavior as well. For example, in many societies, the birth rate is heavily dependent on social economic circumstances. Social economic circumstances are in turn strongly correlated to ethnic background. Ethnic background in its turn is correlated to prevalence of certain genes. So if you are a member of the social economic group with higher than average birthrate for your overall society, then you outstanding fertility is adding to the prevalence in the overall society of certain genes that had been more common in your ethnic group. Over time the genetic composition of the overall society would change to reflect the difference in this aspect of behavior between your ethnic or social group and the rest of society. It doesn't matter if the particular gene in question may not have anything to do with your social economic circumstances or your fertlity. You carry it and you are more futile, so you alter the society's gene pool to more closely reflect yours. This again is evolution.

As to whether this is slow compared to normal Darwinian rates of evolution, I don't think so. Your typical species in fossil record lasts 2-3 million years before going extinct or evolving so much that it is deemed to be a new species. Anatomically modern humans have only been around less than 200,000 year, behaviorally modern humans probably less than 70,000 years. Already we can find in our genes evidence that we've been subjected to strong selective pressure, that certain very recently acquired, behaviorally linked genetic mutations have crowded out other versions of the same gene in very large percentage of human population in just a few thousand years. What is to say we can linger for another 2 million years without accumulating so many behaviorally linked genetic changes as to have effectively become a different species?