An oversimplified proof for evolution
By a non-biologist
Let’s start with some definitions so we know how we’re using these words.
Evolution is defined as:
the change in heritable traits of biological populations over successive generations.¹
any change in the frequency of alleles within a population from one generation to the next”²
Alleles are defined as
one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location. An individual inherits two alleles, one from each parent, for any given genomic location where such variation exists. If the two alleles are the same, the individual is homozygous for that allele. If the alleles are different, the individual is heterozygous.³
Easy Layman Explanation of Evolution
Evolution is easy to explain. Eye color is an allele in the human genome. The primary colors are brown, amber, hazel, green, blue, and grey. Let’s assume, for the moment, that before you were born, the world consisted of a precisely equal mix of each eye color, roughly 16% brown, 16% amber, etc. Your parents have two different eye colors, brown and green. You end up with green eyes. Has the frequency of eye color alleles changed? Yes, it has. Evolution happened.
Selection pressure could be anything from environmental factors to social factors. Maybe the hottest movie star has green eyes, and green-eyed folk get selected more often than other eye colors. The pressure source doesn’t matter, just that something causes the allele frequency to change. This is just the minimum of evolution.
As for the speed of evolution, we’re each an evolutionary experiment. Each human generation, on average, has about 64 mutations from their parent’s DNA⁴. That means we’re each an experiment. Some species have higher or lower mutation rates. However, the mutation rate doesn’t account for all the other ways that the genetic code can get modified, removed, or added.
Additional mechanisms that change our DNA include but aren’t limited to:
— endosymbiosis⁵
— epigenetics⁶
— horizontal gene transfer⁷
— somatic hypermutations⁸
— errors in gene copying⁹
How did body part x spring forth from nothing?
It didn’t. Nothing in evolution says that it’s even possible. Evolution is small changes that add up to significant changes over time. We see this in the evolutionary history of several body parts and plans.
The laryngeal nerve, for instance, went from the brain, past the heart, to the gills in fish. When fish started to walk and become land animals, the laryngeal nerve changed its function, as the gills changed. Because it went past the heart, and the brain and the lungs became farther apart, the nerve became longer. In the giraffe, for instance, it’s 15 feet long. Now, instead of the lungs, it’s connected to our larynx and controls it. It’s what gives us speech and makes giraffes vocalize well after they’ve decided to¹⁰.
This leads to an important question: how many tiny changes add up to a significant change?
How long did it take to evolve the eye?
It only takes about 1800 tiny changes to go from light-sensitive cells to a human eye¹¹. Researchers with a pessimistic view of the evolution of the eye estimate that it only took around 360,000 generations of a species to evolve the eye. In the 550 million years since eyes first appear, they could have evolved 1500 times¹².
Can dogs give birth to cats and other nonsense
To address this, we first have to define what a species is.
Species is defined as:
The largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the [basic unit of classification]( https://en.wikipedia.org/wiki/Taxonomy_(biology)) and a [taxonomic rank]( https://en.wikipedia.org/wiki/Taxonomic_rank ) of an organism, as well as a unit of biodiversity. Other ways of defining species include their [karyotype](https://en.wikipedia.org/wiki/Karyotype), DNA sequence, [morphology](https://en.wikipedia.org/wiki/Morphology_(biology), behaviour, or [ecological niche]( https://en.wikipedia.org/wiki/Ecological_niche). In addition, paleontologists use the concept of the [chronospecies](https://en.wikipedia.org/wiki/Chronospecies) since fossil reproduction cannot be examined.¹³
groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups.¹⁴
Problems with the definition of species
Humans, not nature, determine a species. The definition we use doesn’t always work. That’s because humans attempt to categorize things and organize them despite the chaos of the natural world. There are at least 26 different species concepts.¹⁵
Some species shouldn’t be able to mate, but do. These include, but aren’t limited to:
- Ligers — Lion-Tiger hybrids¹⁶
- Sturddlefish — Russian Sturgeons and American Paddlefish (these two are separated by 184 million years of evolution)¹⁷
- Mules — Horse and donkeys¹⁸
Ring species are also problematic.¹⁹ A ring species occurs when you have a series of connected populations, but the species at the ends of the connection can’t breed anymore with each other.
Let’s say you have a lake that runs north-south. Along its shores, the terrain and other environmental factors differ significantly. A species of lizards moves in at the north end of the lake and begins to expand to the east, clockwise, until the lizard populations meet back up in the north. The northern and eastern lizard populations can breed together, but the northern and southern can’t. Are they the same species? Morphologically, they haven’t changed much, but in a strict definition of the species concepts, they might be.
Nothing in evolution, or the definition of species, says that any group of organisms can spontaneously give birth to a whole new species. This is just straw-manning evolution.
Dogs will always give birth to dogs. However, after enough generations have passed, that dog's descendants may no longer resemble the original breeding pair.
Another example is deuterostomes. Deuterostomes are animals that have their anus’s form before their mouths. This group includes all vertebrates, including humans. Deuterostomes have never stopped producing deuterostomes as children. However, humans, blue whales, and hagfish are not the same species, even though we’re all deuterostomes.²⁰
There’s an excellent interactive site that depicts the entire tree of life: http://www.evogeneao.com/en/explore/tree-of-life-explorer, where you can explore the concept if you’d like.
There are no new species.
Well, there are. Here are two:
Big Bird Finch
This species evolved within two generations, making for a high-speed evolutionary cycle. These finches are also in the Galapagos, the same islands and birds Darwin studied. The new species is from a cactus finch and the ground finch.
Scientists did try and see if the new species could mate with any of the other three species on the island of Daphne Major, and they could not. This is a solid indication of a new species.
The new species has unique songs, habits, and other traits that make them unique on the island. They are also very heavily inbred and number only about 30 birds.²¹
2. Marbled Crayfish
It was first seen in 1995 and is believed to be an accident in an aquarium. Starting in Germany and two decades later, it has spread throughout Europe and Africa.
But some species haven’t evolved.
This is predicted by evolution. If a species has evolved to a point where it’s successful in its environment, then there are no selection pressures. Sharks, for instance, are very well adapted to their environment. There is no pressure on them to change their form or internals. I don’t need a source for this since you can prove it by what I’ve already said about evolution.
One big issue with this claim is that not all changes are to a body plan. The evolutionary change can also be related to things that don’t leave a fossil: sense organs, digestive tracts etc. There’s a whole host of things that don’t leave anything in the fossil record. This doesn’t mean evolution doesn’t happen.
1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4705322/#:~:text=Evolution%20is%20the%20change%20in,as%20the%20last%20universal%20ancestor.
2: https://plato.stanford.edu/entries/evolution/
3: https://www.genome.gov/genetics-glossary/Allele
4: https://en.wikipedia.org/wiki/Mutation_rate
5:https://www.pnas.org/doi/10.1073/pnas.1421389112
6: https://www.cdc.gov/genomics/disease/epigenetics.htm#:~:text=Epigenetics%20is%20the%20study%20of,body%20reads%20a%20DNA%20sequence.
7: https://en.wikipedia.org/wiki/Horizontal_gene_transfer
8: https://en.wikipedia.org/wiki/Somatic_hypermutation#:~:text=Somatic%20hypermutation%20involves%20a%20programmed,transmitted%20to%20the%20organism%27s%20offspring.
9: https://en.wikipedia.org/wiki/Gene_duplication
11:https://royalsocietypublishing.org/doi/10.1098/rspb.1994.0048
12:
13: https://en.wikipedia.org/wiki/Species
14: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1131873/
15: https://en.wikipedia.org/wiki/Species_concept
16: https://en.wikipedia.org/wiki/Liger
17: https://www.livescience.com/impossible-hybrid-fish-created.html
18: https://en.wikipedia.org/wiki/Mule
19: https://en.wikipedia.org/wiki/Ring_species
20: https://en.wikipedia.org/wiki/Deuterostome
21: https://cosmosmagazine.com/science/biology/new-species-evolve-in-just-two-generations/