Speciation, commonly known as macroevolution, is supported by several lines of evidence, including direct observation, genetic mapping and the fossil record. Several populations have been observed in the act of splitting into new species. Comparison of genomic sequences between species are most easily explained as a result of recent common ancestry and an extensive fossil record has yielded numerous transitional fossils.
Macroevolution has been directly observed in a type of flowering plant called the American goatsbeard. Introduced to the Americas from Europe in the early 20th century, three species of goatsbeard began hybridizing in the wild. By the 1950s, they had produced two new varieties that could breed within their own populations but not with the surrounding goatsbeards, which is the criteria for being labeled a new species.
Direct genetic comparison between humans and chimpanzees provides more evidence of speciation. Humans have 46 chromosomes, while chimpanzees and gorillas have 48. Human chromosome 2, however, has distinctive sequences of nucleotides that suggest it is the result of fusion between two chromosomes at some point in the relatively recent past. The most plausible explanation for this fact is that humans and chimpanzees are closely related but diverged into separate species.
The fossil record is rich with transitional fossils demonstrating the development of new species and larger groups. In particular, the transitions from reptiles to mammals, reptiles to birds and apes to humans are well evidenced by fossils.