I was telling the theory of evolution to my friends. But they asked me for the proof. They said, we are not seeing any such transition species at present. Neither we have such evidence for evolution. What should I do? I saw many proofs like archaeoptaryx, but now it has been proved that it is fully functional bird and others are also not supporting the theory of evolution given by Darwin!
I saw an excellent public science talk a few weeks ago. The speaker presented 5 questions which, if you answer yes to, you can only come to the conclusion that evolution exists. Firstly though we should define evolution: Evolution is the change in the inherited characteristics of biological populations over successive generations.
It was one of the best arguments I've seen put forward so I'll try to recreate it here. Put this to them and see what they say - and just in case they say no to any, I've put answers in for you ;) There is no hard evidence for the first four points because they are so damn obvious that if people say no, even after a logic based argument, then all they will ever say is no, they shouldn't need a scientific paper.
1) Do individuals reproduce?
The answer to this is undeniably yes, you were the result of reproduction. Reproduction exists.
2) Is there variation among individuals?
Yes, again this is undeniable. Do we all look and act the same? No. Are some people taller than others? Yes. Some more physically fit than others? Yes. Is everyone's hair or eye color the same? No. See, undeniable. Variation exists.
3) Do some individuals die before they get to reproduce?
Obviously yes. Children unfortunately die (of natural causes) which means they do no get to reproduce. Just go look in a cemetery or open the obituaries page of you newspaper and you'll likely find some one who died before they could have reproduced. Some people also never reproduce, because of life choices or fertility problems. Variance in reproductive success exists.
4) Do offspring resemble parents?
The answer to this is also yes, when two humans reproduce they (normally) produce something that resembles a human. And when that human reaches maturity they will likely look a more like their parents than a random stranger. Personally I was looking at old family photos recently and I honestly though I had found a picture of me marrying my mother, that's how similar my dad and I look. Heritability of variance exists.
5) Does heritable variation lead to differences in reproductive success?
If you've answered yes to all of the above then you really should be answering yes to this one too. As a hypothetical illustrative scenario, imagine two male deer. One has big antlers and one has small antlers. The size of antlers is largely genetically determined. The male with big antlers is seen as more attractive by a female. She chooses to mate with him. She gives birth to his offspring (n=2, 1 male 1 female) who inherit his genes for large antlers. This repeats with several females in the population (n=10). The smaller male has fewer mating events (n=2) and therefore sires fewer males in the next generation. The next generation contains more males with large antlers (n=10) than small antlers (n=2). This is evolution, the change in the inherited characteristics of biological populations over successive generations.
Another example is humans. We know some men have low sperm counts leading to low probability of successful mating. Further, we know that male infertility can be genetically caused for example by Y-linked genetic defects. Therefore we can expect that males with low sperm counts, caused by Y-linked defects, will have fewer offspring than a healthy male (given equal opportunity to mate) and because all males inherit their fathers Y chromosome they too will have low sperm counts. They will be represented at a lower level in the population's next generation. Again, this is evolution.
It then doesn't take much to jump from this to speciation. It involves the introduction of isolating mechanisms. These can be things like geography (allopatric speciation), or sympatric mechanisms like morphology, behavior, or any trait which prevents one group of individuals mating with another.
I'll illustrate first, and take the more difficult type - sympatric speciation. Again imagine our deer population. This time there is variance in sperm morphology, and female reproductive tracts. Males can produce two different types of sperm, one (male type S) is a slow moving but more resistant to the hostile female reproductive tract (because it is resistant to all types of antibody the females can produce), the other is faster (male type F) but less resistant (because it is resistant to only some of antibody the females can produce). Female reproductive tracts vary in the number of different antibodies they produce, one produces "all" that can be produced (female type R) and the other only a subset of the full array (female type W).
What will happen is that type S males will be more successful when mating with type R females because their sperm survive (whereas type F males have no sperm fertilizing the egg). However, type F males will be more successful in sperm competition than type S when mating to type W females. Repeated over many generations, these incompatibilities will cause distinct mating groups which do not overlap, i.e. species.
In reality it is much simpler to demonstrate this with allopatric speciation. Here two groups of one species become isolated by a geographical feature, like a river. Over time these populations evolve differently (because genetic mutation is random and selection might differ on opposite sides of the river). When they get the opportunity to mate after X generations, they can't because they have evolved genetic incompatibilities (offspring fail to survive, eggs can't bee fertilized).
One of the absolute classic examples is an experiment using fruit flies by Diane Dodd. In her experiment she reared a population in two groups, one on starch based food, and one on maltose based food. After many generations (35 I think) the two groups showed mating preference, which is a reproductive isolating barrier, within their groups (mating pairs were more often formed from within treatments). Here is the paper.
Picture from http://evolution.berkeley.edu/
Despite evolution is generally macroscopically appreciable after a long time, there are some examples observable right now.
A classic example is the evolution of the peppered moth (Biston betularia) in the last two hundred years. Originally the predominant color was white, which camouflaged them against light-coloured trees such as Betula plants, while dark-colored moths were rare. During the Industrial Revolution in England the pollution blackened many trees, causing most of the light-coloured moths to die off from predators. The black-coloured ones (called carbonaria) flourished because of their ability to hide on the darkened trees.
The best example about whole species evolving is the ring species. Here is a good definition from wikipedia:
In biology, a ring species is a connected series of neighbouring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" species. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing a "ring".
Ring species provide important evidence of evolution in that they illustrate what happens over time as populations genetically diverge, and are special because they represent in living populations what normally happens over time between long deceased ancestor populations and living populations, in which the intermediates have become extinct. Richard Dawkins observes that ring species "are only showing us in the spatial dimension something that must always happen in the time dimension."
You can continue the reading at the related wikipedia article.
The best proof of evolution is not in the fossil record, but perhaps in the living things you see around us right now.
For instance the rise of antibiotic resistant bacteria is the direct result of selection. The environment for the bacteria changed - we introduced antibiotics. The vast majority of the bacteria die, but eventually the survivors are resistant- just in the space of a few years.
Adaptation and even speciation is occurring around us and can be observed directly.
A case that all of has seen, and was one of the most important to Darwin's argument in the Origin of Species is how we breed domestic animals. By selecting animals with characteristics they find desirable, all sorts of animals are created by the use of selection - breeding the animals you want and then not breeding animals with characteristics that are not desirable. Cats, dogs, horses, sheep - using selection any animal you want can be modified nearly to the point you can't recognize it. This is a multibillion dollar industry when you think of all the livestock and pet breeders in the world.
The most famous scientific experiment along this lines is Dmitry Belyaev's domesticated fox experiment where over 40 years the foxes who were the friendliest to humans and bred them together. As a control experiment the most hostile foxes were also bred together. The result is an animal which is as friendly as a golden retriever, even though no fox had ever before been taken as a pet.
There are dozens of other stories. Selection for breeding plants is another such success story. Though it takes more work and time, Selection is as reliable as electronics as a technology.
Making someone believe something that they don't want to is much harder though.
Of course you dont see a transition species at present! A transitions species is what existed between two other species. When it "becomes" the new species, the transition species no longer exists. Transition species only exist in the past. Its also important to remember that species are a spectrum. When we divide things up into discreet species it makes it seem all neat and tidy but really it is not because of the large amount of variation that exists within a species. When the variation becomes so great that certain members of the species may not be able to interbreed, we break it into two species.
I also do not see why you need to visually see evolution to believe it exists. The strongest evidence can be found in DNA or protein sequences. Look at any conserved protein and see the similarities. I will give you a link that shows the difference between the mouse and human version of a protein called p53. p53 is studied a lot because it is thought to have a role in cancer. Im not even sure if p53 is considered a "highly conserved" gene, but look at how similar it is!
How many generations difference do you think there is between a mouse and human? [remeber humans did not evolve from mice, they just had a common ancestor, so what I mean is how many generations have elapsed since the last common ancestor]? It is estimated that mice / humans disverged some 70 million years ago. Lets say a generation (age difference between parent and child) is ~30 years in humans (it is much much much much less in mice but lets forget about that) that means there were some ~2 million generations, and thats being conservative. This website claims there are 74 de novo[new] mutations in humans each generation. Technically this is not all mutations but again we are being conservative. So that is about a 150 million mutation difference between humans and the ancestor that became both humans and mice
My question to you is this: Look again at the similarities between human and mouse p53. You see how there are some differences? Dont you think it is entirely possible that the differences can be accounted for after having 150,000,000 chance mutations?**
Now imagine this happening to every gene, not just p53. That is evolution
*Not sure how long this link will be valid but you can see the sequences at these links and do the alignment yourself here
**Actually double that to account for mouse evolving from the common ancestor but like I said, wanted to be conservative
There are six different types of evolution and they all happen on different levels.
Cosmic evolution- the origin of time, space and matter. Big Bang
Chemical evolution- the origin of higher elements from hydrogen.
Stellar and planetary evolution- Origin of stars and planets.
Organic evolution- Origin of life from inanimate matter.
Macro-evolution- Origin of major kinds.
Micro-evolution- Variations within kinds. Only this one has been observed. For instance poodles and great danes are descendant from the same thing. A wolf.
Are you asking about macro evolution or micro evolution? Or one of the other 4?
Speciation does not show macro evolution in any way, shape, or form. And the ring species you refer to moths changing colors, that is micro evolution. A moth changing into another moth would even be micro evolution.
Man thought up species and defined them. If it looks like a duck and quacks like a duck, it didn't evolve into a different animal because it changed the color of it's feathers.