What scientific evidence supports Darwin's theory of evolution by natural selection?

Answer 1

Darwin had considerable evidence at his disposal. The most famous would be the finch beaks on the Galapagos Islands. But he also noted graduated geographic differences in pigeons, as well as traits bred by pigeon fanciers. Fossils of giant sloths indicated these creatures and forms and varieties long extinct.

Probably the single biggest piece of evidence was the fact most species fit into a nested hierarchy of forms, highly indicative of shared (or common) ancestry.

Answer 2

We have fossil stromatolites billions of years old, proving the oceans teemed with simple single celled organisms for eons before the first multicellular marine organisms came into existence some 650 million years ago. We know jawless fish predate jawed fish, and sarcopterygian lungfish predate the fishapod Tiktaalik. Tiktaalik predates the earliest devonian amphibians, which had to await the colonization of land by early flora and insects for their to be new niches for them to exploit.

All of this fossil evidence points to a gradual evolution of the species, just as Charles Darwin described. Since the publication of his theory we have developed whole new lines of evidence in support of evolution, such as genetics and cladistics. We have observed speciation and evolution occur in the wild, and artificially in laboratories at rates higher than would be required to explain the diversity of life we now find.

There are also numerous studies of genetics lending support to Darwin's theory. Pseudogenes and viral DNA insertions both are indicative of common ancestry. Humans have 23 pairs of chromosomes, whereas other old world primates have 24 pairs. We have identified the pair of chromosomes that fused to reduce our number. These fused chromosomes even possess remnants of the telomeres--DNA sequences marking the ends of a chromosome--embedded where the original pairs joined. You could hardly hope for more compelling evidence for common ancestry between humans and simians, but there is much more evidence besides.

Answer 3

A long-term experiment demonstrating evolutionary change in bacteria is found in the work of Richard Lenski. Dr. Lenski's team has maintained a continuous lineage, descending from a single E coli colony, for twenty years. The E. coli were passed in 12 independent populations but subjected to the same environmental stresses. The team kept frozen stock to document any mutations over time and keep a living history of the changes leading to the present generation in 12 separate populations.

One population of the 12 began to display a shift in its metabolism. It was not a contaminating wild type of bacteria it was an E coli but one able to feed on citrate rather than glucose. This was not from a plasmid introduced to the bacteria nor is it an ability E coli have naturally.

In order to figure out what happened they returned to the frozen stocks. They could see the rate the population changed from mostly glucose eaters to mostly citrate eaters over time. They sequence the genetic changes documenting every mutation the E coli progressed through until, unlike wild type E coli, the microbe can use citrate as their carbon source.

The final result is 19 citrate using mutant strains with alterations in their (pykF) and nadR genes that can be used as markers to identify their parent population from the 12 and show descent with change.

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Answer 4

He found fossils of creatures from the past that are similar (but not identical) to creatures today. There are numerous fossils of transition species. Some of the most famous are devonian amphibians like acanthostega and eogyrinus, the fish/amphbian tiktaalik, and the bird/reptile transition archaeopteryx.

Molecular Biology also supports Darwin's theory in terms of inherited sequences.

Answer 5

There was already evidence that life was variable, species were variable, before Darwin plunged into his great evolutionary adventure of discovery for the explanation of life's form and diversity. What Darwin did was hypothesize Natural Selection as the 'driving force' of evolution and as an explanation for adaptation. Experiments have been done with brown mice and black mice that live on light or dark soils respectively. Take a mouse, experimentally, and put it on a ground surface that contrasts with its shade of coat and it is more likely to be nailed by a predator. Then there is the famous guppy experiment of Endler. Put guppies in a predatorless pond and they develop bright colours (sexual selection takes over). Put guppies in a pond where they can be chomped by a present predator and they evolve duller, more camouflaged colours. Those are evidences for Natural Selection. For Selection of any kind to work, there has to be natural (genetic) variation. Darwin knew nothing of Mendelian genetics but certainly knew there was variation. He bred pigeons and certainly knew of the diversity of dogs and other domestic animals, all examples of variation made visible via "artificial" Selection as he called it. Pigeons and dogs are variable, as are cheetahs, leopards, and other jungle and mountain cats in the wild. There is variety in wild wolf populations also, with a dozen or more recognized subspecies. The variation today is the fuel of evolution and speciation and Natural Selection.

Where did all today's life come from? We know birds evolved from dinosaurs. Archeopteryx might be an over-enthusiastic announcement of "THE MISSING LINK" (the real transitional form) between dinosaurs and birds but it certainly was an intermediary, or "transitional" form. Many carnivorous dinosaurs are now known to have been bird-like in the feather department. And perhaps Tyrannosaurus rex was feathered too! We know that man is a hominid, and hominids are primates. The jaw shape of australopithecines is transitional between apes and humans, not to mention the brain size (inferred from skull size). Australopithecines thus look suspiciously transitional. And Darwin predicted, simply from morphology, that the ancestors of humans would be found in Africa, and this was confirmed.

Another series of transitional species are the relatives of Tiktaalik roseae that depict changes from sarcopterygian fish like the Latimeria chalumnae's ancient ancestors to the amphibian forms found in the Permian.

Common ancestry is a big thing in evolution. Every taxon has a common ancestor. All life has a common ancestor. Imagine the common ancestor of terrestrial vertebrates having leg bones. It diverged and speciated and gave rise to all of the world's terrestrial vertebrates from about the Triassic to the present. All mammals have the same leg bones (ulna, radius, phalanges etc), all warped by Natural Selection into forms suitable to their way of life. This is evidence for common ancestry. All angiosperms have petals and sepals and stamens and styles, all warped and fused and whorled in different ways by Natural Selection, but the common presence of all can be explained by common ancestry. And all life uses RNA, all life is composed of at least one cell, uniting all life on the planet.

Recently, chromosomes have flown dramatically into view and knowledge. Humans have 23 pairs of chromosomes and chimpanzees and gorillas have 24 pairs. Therefore, one chromosome had to have become fused on the way down the populations and species between the Chimpanzee-Human common ancestor and the human. And, we can see that there is a fused chromosome, fused since the apes, in humans, chromosome 2!

Answer 6

Common descent is the theory that all living organisms on Earth descended from a common ancestor. Biologists have evidence that all life developed from a common ancestor that lived just under 4 billion years ago, and the concept is accepted by virtually all scientists working in the field. The structures and functions of all living organisms are encoded in the same basic nucleic molecules, DNA and RNA. Similarities in amino acid sequences between various organisms also suggest common descent, and the fossil record also shows cases in which one plant or animal type evolved into different types over time. The details of this process are shown in clade diagrams

Do fossils validate common descent?Although fossils are usually not direct evidence in favour of common descent, a purely anatomical resemblance to living species is a form of strong supportive evidence. Some more recent fossils contain traces of tissue or DNA that can be used to determine in what way the fossil is related to living species. As mentioned below, this offers direct evidence for evolution. Transitional formsWhile creationists often claim that no transitional forms have been found, numerous transitional forms have been found over the years.

Of course, one could always move the goalposts and keep asking for more transitional forms between other transitional forms. However, fossilization is the exception to the rule (usually, cadavers decay completely) and that seismic, volcanic, tectonic and human activity have destroyed or buried many fossils.

"Transitional forms" is a bit of a misnomer anyway. A case can be made for all forms being transitional or none. All forms alive today seem to be very well adapted to their environment, and none looks obviously "transitional". The same would certainly have been valid in the past; only with the benefit of hindsight can they be labeled "transitional". The only forms that are not obviously "transitional" are those with no living descendants or those that have survived to this day without change. To put it another way, evolution does not occur in between periods in which no changes occur; though it may be slow with occasional bursts in speed, mutation and natural selection are ongoing processes

Answer 7

There are hundreds of independent lines of evidence, each boasting thousands of independent studies and observations. The main categories of these independent lines are:

• Observed evolution, divergence at the morphological, behavioural and genetic level.
• Observed speciations in various stages of divergence, including ring species.
• The nested hierarchies of biology as demonstrated by the morphologies, behaviours, embryological development and genes of living species.
• The presence of pseudo-genes in the genomes of living species, fitting this pattern of nested hierarchies even though they're not selected for.
• The presence of atavisms during and after embryological development that coincide with this pattern of nested hierarchies.
• The neat fit of the fossil record with the abovementioned nested hierarchies.
• The presence of diverging progressions of traits throughout the fossil record, again fitting the nested hierarchies of biology.
• The presence of morphological intermediates in the fossil record (ie. "transitional fossils") again fitting the same set of nested hierarchies.

Answer 8

New data from genetics, physics, and biochemistry. Scientific evidence support the theory that living species descended with modification from common acestors that lived in the past

Answer 9

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