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37

Very intresting question. The problem is that animal intelligence is hard to measure not only for scientists, but probably also for the potential mate. Paradoxically, that is why selection for intelligence, if it occurred, may be very strong. One has to be smart in order to recognise smart behaviour, so preference and preferred feature are strongly connected....


37

This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed. Long Story Short You're question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" ...


37

During the process of selection, individuals having disadvantageous traits are weeded out. If the selection pressure isn't strong enough then mildly disadvantageous traits will continue to persist in the population. So the reasons for why a trait is not evolved even though it may be advantageous to the organism, are: There is no strong pressure against ...


24

There's always the most obvious: Evolution is chance. Some traits allow an individual to have a higher chance to produce offspring. That doesn't mean individuals with that trait have more offspring, not even on average, unless the law of large numbers applies. A randomly mutated perfect squirrel could appear, and since it's only one, it gets run over by a ...


20

Mathematician/computer programmer's answer here: There is a continuum of different animals — in fact it's pretty fair to say that every animal occupies a different place on this continuum. They're just not uniformly distributed over the continuum; they're clustered around forms that are most likely to survive and reproduce, and the lowest-energy paths ...


18

To get a non-circular answer to why humans and other mammals have only two sexes, it's helpful to take a look at our evolutionary history. While mammals possess several adaptations to a terrestrial life cycle, including internal fertilization and gestation, which require substantial anatomic specialization between males and females, these are all secondary ...


17

I am not sure I'll answer your question so let me know if I miss your point or if I help! To start with, you might want to read this answer on the semantic difficulties behind the concept of species What factors determine whether some species "stick"? Natural selection is nothing but differential fitness (fitness is a measure of both reproductive ...


14

I looked up winglets so I had context for this answer. I'm interpreting winglets as the vertical tips at the end of airplane wings. If so, then you are correct. The spread primary feathers of soaring birds like eagles function as winglets (Tucker 1993). Airbus has a biomimicry web page devoted to some of the biological designs, including winglets, they ...


14

Change in genetic variance From what I have been taught, Natural Selection (or even Artificial Selection) is great for panning favorable genes from a species and bringing them to the fore, however, it does not introduce new genetic changes. Yes, you are pretty much right. In a given population, directional selection will ultimately reduce genetic ...


13

Charles Darwin formulated his theory after travelling the world aboard the Beagle, here's the route. He found the Galapagos Islands particularly inspiring, 'The natural history of this archipelago is very remarkable: it seems to be a little world within itself.' This is a more detailed account of his relationship with the Galapagos islands, and ...


13

Because evolution is an effect, not a cause. That is, there's no "God of Evolution" out there deciding that this or that trait would be beneficial to a species, and deciding to add it. Evolution just works* on whatever random variations happen to come along. *And as others have pointed out, it works statistically, not deterministically.


12

Nothing happens to them. Organisms exist. They breed with other organisms who are genetically compatible. We humans might try to categorize them according to certain traits, but our labels are just labels, biology isn't governed by them. Over time, we might see that a population used to have one trait, and its descendants no longer have it, they look ...


12

About your question This kind of very basic question has the drawback to need a very long answer. In consequence your question might get some close vote. I'll do my best to help but you might want to look at some source of information as an introduction to evolutionary biology. A book eventually or Khan academy maybe. Darwin's evolution theory The ...


10

Typically when both new and old species still exist it is because evolution pushed the new one into a different habitat or role. As a hypothetical example reef fish vs deep water fish and their relative size. Lets say deep water fish evolved into reef fish, but we still have deep water fish. So there were deep water fish that were a little smaller than ...


10

I accidentally wrote a lot! I first discuss the term Darwinian evolution. I then describe the main evolutionary processes insisting on the two elements of interest in your question, that is mutations and natural selection. At the end I directly address your two statements and bring a few more complications into the subjects. Did you say Darwinian evolution?...


9

The idea that we only love our family according to biology is not true, but its also not clear what people mean by the word 'love'. There are many ways to interpret that word! Hope this doesn't totally suck any romantic ideas out of you, but metaphysical concepts of love and romantic ideas of love are not always relevant when you talk about biology. A ...


9

The question is probably more complicated than it seems because, if I am not wrong, the word adaptation here is understood at the group level. Definitions of adaptation Unfortunately, there is not such thing as a single, standard definition of adaptation. But for most cases the accurate definition the author is using is not of much importance as all of the ...


9

The logical assertion "winglets have not happened in a long time, therefore they are not advantageous" is incorrect. It is possible for an advantageous trait not to evolve even when advantageous, if there is no "path" to it. The trait only occurs gradually, in small incremental steps. If intermediary steps are harmful, the trait will not occur, even if the ...


8

Its pretty much impossible to predict what will happen in the evolution of species. Evolution is a parallel search with millions (or in the case of humans 8+ billion) of threads. Our adaptive capacities have never been fully understood and will always surprise us I think. Of course that doesn't stop people from trying! The prediction you mention is ...


8

I just wanted to add that although we are pretty confident that domestication of wolves created domestic dogs in pretty short order. In addition to the fact that they can still interbreed and the taxonomical resemblence of dogs to wolves and finally the genome sequence, probably the most awesome evidence is the domestication of the silver fox. Russian ...


8

According to Serpell, 1995 (http://books.google.co.uk/books?id=I8HU_3ycrrEC, page 8), wolf bones in association with human bones have been found from as early as the middle pleistocene (126,000–781,000 years ago). I think we're talking about more than a few centuries here :) It's still relatively little in comparison to naturally selected evolution, but that'...


8

Presumably this means that at least some grey haired humans have noticeable reproductive advantage, or maybe they had it in the recent past. No it doesn't. Natural selection is not that strong, it doesn't optimize every single possible physical trait towards maximum reproducing. And as others have mentioned, having lots of grey hair usually happens ...


8

There are two possibilites with evolutionary processes: The development either never went into this direction or it brought no advantages. Besides this two possibilities the claims from the other forum are wrong. Birds (not all of them though) do have winglet-like structures. If you look at big birds, you can see feathers on the end of the wings looking like ...


8

Below are reasons I can think of. The list is not an exhaustive and there are some conceptual overlaps. I have to say it is kind messy but one can hardly make a list without overlap for this question. The trait seems advantageous but it is not, maybe due to its effect on another component of fitness (trade-off). It sounds to me to be the most likely ...


7

Galápagos islands are one of few islands with a unique fauna and flora. This can only happen when the distance to other land is great enough, and when the island exists long enough that flora and fauna could grow (volcano islands are sterile for a long time). Now Galápagos is even more unique because it is comprised of several islands that are distant ...


7

The evolution to the current state of life on earth has occurred through some 3.8 billion years. During this time it has gone from the most basic forms of life, simple self-replicating units, to the complex beings we see today. Evolution, the process of change within a collection of units, is caused by 4 factors, mutation, selection, drift, and gene flow. So ...


7

More specifically, the lack of observable gradual change between species. Most significant phenotype differences occur over several thousand generations, which means several thousand years on up. While we certainly can create experiments where a controlled form of evolution occurs within a very small time-frame, I'm going to assume that you're not ...


7

A trait is said to be adaptive when it causes fitness to increase. Fitness is generally understood as the (relative) contribution to future generations in terms of offspring or genes. The trait is selected for by the environment and hence increases fitness. In the paper of Dey et al. this is the fitness of the parent birds. Hatching asynchrony causes size ...


7

Short answer version: It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation. No, it's not. Despite what your ...


7

You're right that the mutation must be in a germ cell in order to be passed on. Most errors are introduced during DNA replication (at a rate of around 10-10), which occurs a number of times between the zygote stage and mature gametes. This book estimates that there are 24 divisions between zygote and egg and 23n+34 divisions between zygote and sperm, where n ...



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