Topic Editor: Steven Novella
There are many forms of creationism but at their core they all share a denial, to some degree, of evolutionary science. Creationism is therefore a pseudoscience and a form of denialism.
The various forms of creationism include:
Young Earth Creationists – believe the earth is 6,000-10,000 years old, based upon a literal interpretation of Genesis. YECs believe that God created all living things essentially in their current form. They deny all of evolution, except perhaps for what they call “microevolution”, or minor adaptations to the local environment. Of course, evolution is nothing but adaptation to the local environment, extrapolated over billions of years.
Old earth creationists believe that the world is billions of years old, but still deny various aspects of evolution. Some deny common descent – that all species are phylogenetically related, and instead believe that life arose through a series of separate creations. Others accept that life evolves and is related through common descent, but deny random mutations and natural selection as the mechanism of evolution. They believe that a supernatural force was necessary to push evolution forward.
In this latter camp are many of those who espouse so-called Intelligent Design, which is really just another name for creationism or evolution denial. They argue that evolution could not happen, for various reasons, and therefore a supernatural agent was necessary.
Finally, there are those who accept the scientific consensus on the fact and mechanism of evolution but hold out belief that evolution unfolded according to the will of God – that evolution was simply God’s mechanism for creation.
Meanwhile, the evidence for evolution is robust and growing, leading to its overwhelming acceptance among scientists. To quickly summarize this evidence:
Fossils – The fossil record shows the appearance of new species over time, their persistence for a time (on average about 2 million years) and then their disappearance. But more importantly, there is a distinct pattern to the fossil record in that new species appear morphologically related and derived from older species. The fossil record reveals a bush of hierarchicaly nestled groups – exactly what we would expect if life arose through evolution and common descent. Further, there are no fossils that falsify evolution – no horses mixed in with Cambrian fossils.
There are also many transitional fossils (in reality all fossils are transitional, but specifically there are those that bridge gaps between extant species). Despite the numerous false claims by creationists, and as predicted by evolutionary theory, paleontologists have found fossil species that are transitional between fish and terrestrial animals, reptiles and mammals, reptiles and birds, land mammals and whales, ape ancestors and humans, and many many more.
Genetics – If we examine the genetic relationship among species we also find a pattern of relationships that closely resembles the bush of life drawn through morphology. At a fine level of detail, of course, there are anomalies but the overall pattern is clearly evolutionary. For example, if we pick a protein like hemoglobin we find that the more closely related two species are the more similar their hemoglobin – even if we look at silent changes in the DNA sequence in the gene for hemoglobin. There is no functional reason for this pattern – only an evolutionary reason makes any sense.
Development – While embryos do not pass through the adult stages of earlier species (and old idea now rejected), development does carry the scars of evolution. Specifically, embryos do not develop directly and efficiently into babies but rather the developmental process takes many complex and unnecessary twists and turns. Developmental pathways, however, can be explained by evolutionary contingency – evolution often works by tweaking the process of development, taking it down different paths.
Morphology – living organisms also carry the tell-tale signs of their evolutionary past, usually evidenced through suboptimal design due to the constraints of evolutionary history. The eye is an excellent example (see reference below) – in vertebrates the retina is literally backwards, the light sensing layer is below the vascular and other layers, causing unnecessary problems.
There are also many vestiges of our evolutionary past. Cave salamanders retain stunted and useless eyes in their dark environment. Chickens retain genes for teeth that never get expressed. Pandas have a thumb that is actually an enlarged wrist bone.
Selection and mutation – there is now also copious direct evidence that beneficial mutations occur spontaneously in nature, and that beneficial mutations can be selected for and spread through the population. There is even evidence for contingency – multiple mutations working together to create a new adaptive trait. So there is direct evidence for every aspect of evolution through natural selection.
Please be patient as we build this resource. In particular the key research we link to below – we obviously cannot summarize the thousands of published articles that constitute the evidence base for evolution. Rather, we focus on recent high quality representative studies that establish important principles of evolutionary theory.
- A Few Questions about Evolution (Steven Novella, 8/09)
- Another Gap Filled – More Evidence for Eye Evolution (Steven Novella, 12/07)
- Answering the ID Crowd (Steven Novella, 09/07)
- Buchanan’s Inane Rant Against Darwin (Steven Novella, 7/06)
- Buckley on Darwin (Steven Novella, 02/07)
- Creationists, Mechanical Engineers, and the Second Law of Thermodynamics (Steven Novella, 4/01)
- Creationists Run Aflow of the Evidence (Steven Novella, 1/99)
- Design, Evolution, and more Semantic Nonsense from ID Proponent, Michael Egnor (Steven Novella, 04/08)
- The Design Interference (Steven Novella, 10/02)
- The Evolutionary Rubes Strike Back (Steven Novella, 04/07)
- Evolve This! – Why We Should Care About Evolution and Creationism (Steven Novella, 10/04)
- Evolving Mice (Steven Novella, 09/09)
- The Expelled History Fallacy (Steven Novella, 4/08)
- He May Be a Neurosurgeon But He’s No Evolutionary Biologist (Steven Novella, 03/07)
- Hugh Ross’s Testable Creation Model (Steven Novella, 04/07)
- Intelligent Design and the Argument from Ignorance (Steven Novella, 07/07)
- Intelligent Design is Not Science (Steven Novella, 04/08)
- Intelligent Design – Response to Behe (Robert & Steven Novella, 11/05)
- Is Intellgient Design Falsifiable? (Steven Novella, 04/08)
- Irreducible Stupidity: As If We Needed Another Example (Steven Novella, 06/07)
- The Judgment of Tiktaalik (Steven Novella, 11/07)
- Ten Major Flaws of Evolution – A Refutation (Steven Novella, 09/07)
- More Witless Self-contradiction from the Discovery Institute (Steven Novella, 4/08)
- Natural vs Artificial Selection and ID Propaganda (Steven Novella, 12/07)
- Non-Science in Dating the Earth (Chuck Roche, 5/04)
- Responding to Behe and Irreducible Complexity (Steven Novella, 4/99)
- Scientific Proof and Evolution Denial (Steven Novella, 07/07)
- Why ID Should Not be Taught in Science Class (Steven Novella, 09/07)
- Episode #97 – Creation Museum Opens
- Episode #99 – Creationism Poll
- Episode #105 – Brain Evolution
- Episode #124 – Information Theory
- Episode #126 – Creationists New Strategy
- Episode #132 – Creationist Research Journal
- Episode #134 – Interview with PZ Myers, Bat Evolution
- Episode #140 – Interview with Eugenie Scott
- Episode #141 – Expelled Again
- Episode #143 – Age of the Earth
- Episode #145 – Evolution Freedom Law in Florida
- Episode #146 – Misconceptions about Evolution
- Episode #148 – Radiometric Dating of Mt. St. Helens
- Episode #152 – Bacteria Evolve
- Episode #154 – Creationism Bill Passes in Louisiana
- Episode #155 – Conservapedia Denies Evolution
- Episode #156 – Tiktaalik
- Episode #165 – Creationism in the UK
- Episode #172 – Junk DNA
- Episode #183 – Science Education in Texas and Lousiana
- Episode #184 – Evolution – Lizards and Fire Ants
- Episode #192 – Evolution Education in Texas
- Episode #197 – Walking Seal
- Episode #200 – Missing Link Ida
- Episode #201 – RNA World, Polonium Halos
- Episode #202 – Texas Update
- Episode #209 – Thomas Jefferson and Evolution
- Episode #215 – Evolving Mice
- Evolution: What the Fossils Say and Why it Matters (Donald R. Prothero, 2007)
- The Greatest Show on Earth: The Evidence for Evolution (Richard Dawkins, 2009)
- The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution (Sean B. Carroll, 2006)
- The Triumph of Evolution: and the Failure of Creationism (Niles Eldredge, 2000)
- Why Evolution is True (Jerry A. Coyne, 2009)
- Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body (Neil Shubin, 2008)
- Evolution 101 Podcast (Zachary Moore)
- Free Inquiry Creationism Resource
- The National Center for Science Education
- The Talk Origins Archive)
(Note: this is not meant to be an exhaustive list of evidence but a smattering of representative papers presenting key evidence for evolution.)
Blount ZD, Borland CZ, Lenski RE. 2008 Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli. Proc. Natl Acad. Sci. USA 105, 7899–7906.
Summary: This elegant and thorough research documents the evolution of E. coli bacteria in the lab over 20 years. Specifically they grew 12 strains of E. coli is a glucose limited environment but rich in citrate – an alternate carbon source that E. coli cannot normally use. After 31,000 generations on strain finally evolved the ability to use citrate, and they thrived. The researchers went back through the generations (because they saved them along the way) and found that the mutation allowing use of citrate was dependent upon two prior mutations.
This research not only establishes in a thoroughly observed laboratory setting that random mutations may lead to the acquisition of a new and useful ability, but the role of contingency in evolution. This directly contradicts the notion of irreducible complexity as put forth by Behe.
Daeschler E B, Shubin NH, Jenkins FA. A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature 440, 757-763 (6 April 2006) | doi:10.1038/nature04639
Summary: This is a description of Tiktaalik – a devonian fish with transitional features of land-based tetrapods. Specifically:
Although the body scales, fin rays, lower jaw and palate are comparable to those in more primitive sarcopterygians, the new species also has a shortened skull roof, a modified ear region, a mobile neck, a functional wrist joint, and other features that presage tetrapod conditions.
It is also notable that the researchers were specifically looking for a specimen like Tiktaalik – evolutionary theory predicted that a fish with similar features should exist in the Devonian era, and so the discovery of Tiktaalik was a powerful validation of evolution.
Linnen CR, Kingsley EP, Jensen JD, Hoekstra HE. On the Origin and Spread of an Adaptive Allele in Deer Mice. Science 28 August 2009: Vol. 325. no. 5944, pp. 1095 – 1098, DOI: 10.1126/science.1175826
Summary: These researchers demonstrate the occurrence of a de novo mutation in deer mice that has arisen in the recent past (about 4,000 years ago), after the geological appearance of sand dunes. The mutation allowed the normally dark haired mice to develop lighter sandy-colored hair for better camouflage in the new environment. This demonstrates the ability of random mutations to provide selective advantage, and for that selective advantage to cause the spread of the new mutation throughout a population.
Mead LS, Mates A. Why Science Standards are Important to a Strong Science Curriculum and How States Measure Up. Evolution: Education and Outreach. Published online: 7 August 2009
Summary: Reviews US state science standards with attention to their treatment of evolution and the historical science, with attention to the inclusion of creationist language.
Rohner N, Bercsényi M, Orbán L, Kolanczyk ME, Linke D, Brand M, Nüsslein-Volhard C, Harris MP. Duplication of fgfr1 Permits Fgf Signaling to Serve as a Target for Selection during Domestication. Current Biology, 03 September 2009, doi:10.1016/j.cub.2009.07.065
Summary: This study shows that zebra fish retain an unaltered copy of the fgfr1 gene while a mutation in the copy of the gene is responsible for the phenotype of mirror scales. This evidence supports the principle that gene duplication is an evolutionary mechanism that increases the amount of genetic information in a species, and allows one copy to retain the original function of the gene while the other copy is free to mutate and experiment with new functions.
Thewissen JGM, Madar SI, Hussain ST. (1996). Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan. Courier Forschungsinstitut Senckenberg 191: 1–86.
Summary: This paper presents the fossil evidence for Ambulocetus natans, the so-called “walking whale.” The link also describes other fossils transitional between land mammals and cetaceans. For years creationists crowed that there was a lack of transitional fossils between land mammals and whales, as if the lack of a complete fossil record called evolution into question. Now creationists have quietly dropped this from their mantra as a beautiful sequence of fossils from land mammal to modern whale has been found and described. Ambulocetus is as close to a half-whale/half-land mammal as you can get – a smoking gun of a transitional species.