Evolution is both fact and theory
In science, the word "theory" doesn't mean a guess. It means a well-tested explanation that is supported by a massive amount of evidence—just like the germ theory of disease or the theory of gravity.
Evolution is unguided but not random
Evolution operates through four mechanisms—mutation, natural selection, genetic drift, and gene flow—that together produce adaptation without foresight, plan, or purpose.
Evolutionary leftovers in the human body
The human body contains dozens of vestigial structures—anatomical features inherited from ancestors in which they served important functions but which have lost all or most of their original purpose in modern humans.
Genetic change creates new functions
The majority of mutations are selectively neutral—neither helpful nor harmful—and accumulate at a roughly constant rate that serves as a molecular clock for dating evolutionary divergences.
Human chromosome 2 is two fused ape chromosomes
All great apes—like chimpanzees, gorillas, and orangutans—have 48 chromosomes (24 pairs), but humans only have 46 (23 pairs). Based on evolution, scientists predicted that two ape chromosomes must have fused together to form a single human chromosome.
Human DNA is 98.7% identical to chimpanzee DNA
The 2005 Chimpanzee Sequencing and Analysis Consortium found that human and chimpanzee genomes are 98.77% identical at aligned nucleotide positions, confirming chimpanzees as our closest living relatives.
Human embryos develop and lose tails, gill arches, and lanugo
Human embryos develop pharyngeal (branchial) arches that are homologous to the gill arches of fish; in humans these structures are remodeled into the jaw, middle ear bones, and throat cartilages rather than forming gills.
Humans carry broken vitamin C genes
Humans and all other simian primates lack a functional copy of the GULO gene, which encodes the enzyme required for the final step of vitamin C biosynthesis. The remnant of this gene—a pseudogene—sits on human chromosome 8 with the same pattern of missing exons found in chimpanzees, gorillas, and orangutans.
Natural selection builds complexity
Natural selection is not merely a filter that removes the unfit; acting on heritable variation over many generations, it accumulates beneficial changes that build complex structures incrementally, as demonstrated by the step-by-step evolution of the camera eye and the bacterial flagellum.
Shared endogenous retroviruses
Approximately 8% of the human genome—roughly 98,000 ERV elements and fragments plus their associated solo LTRs—consists of endogenous retroviral sequences: the remnants of ancient retroviral infections that became permanently integrated into the germline DNA of our ancestors.
The earth is 4.5 billion years old
The Earth is 4.54 billion years old. Scientists didn't just guess this number; they calculated it using multiple independent dating methods that all give the exact same answer.
The origin of life is a chemical problem
Evolution and the origin of life are two completely different things in science. Evolution explains how life changes after it already exists. The origin of life (called 'abiogenesis') tries to figure out how dead chemicals turned into living cells in the first place.