When the gene sequences of mitochondrial cytochrome oxidase II are compared (Ruvulo, 1994), there are variations in the sequences found in humans, in chimps, in gorillas, in orangutans, and in gibbons. While humans may not all have the same sequences, their sequences are more similar to each other than any one is to the sequence of any other ape. For that reason, all humans seem to be related, that is, they are descended from the same ancestors and their gene sequences are modifications of the same ancestral sequences. In the same way, each species of chimpanzee contains sequences that are related to each other and the same can be said for gorillas, orangutans, and gibbons. Similarities can be extended above the species level. The two species of chimpanzee seem to be closely related to each other, that is, both species are descended from the same ancestors. Human and chimp sequences are more similar to each other than they are to any other ape (or animal, for that matter). Not only do chimps seem to be the closest relatives of humans, humans seem to be the closest relatives of chimps.
Notice that the evidence suggests a hierarchy of similarities—the variation between species is merely an extension of the variation within a species. Most of those who oppose evolution would agree that the two species of chimp have evolved from a common ancestor but that humans are completely unrelated to them. Some have written that chimps, gorillas, and orangutans have descended from a common ancestor but that humans are completely unrelated to them. This creationist pattern—that one can identify “kinds” which are equally unrelated to each other and in which humans are separated from other animals—is simply not observed.
The same general pattern of relationship is observed when the sequence of a nuclear gene is examined (28S rRNA; Gonzalez, Mol. Biol. Evol. 7: 203-219; 1990).
The same general pattern of relationship is observed when noncoding DNA which does not contribute to an organism’s phenotype is used.
--yhglobin upstream and downstream flanking regions; Miyamoto, 1987.
--noncoding DNA sequence data;Williams, Mol. Biol. Evol. 6: 325-330, 1989
Other studies show that apes are more closely related to
each other than any of them is to any
--DNA-DNA hybridization; Sibley, J. Mol. Evol. 20: 2-15
--various old world monkeys yield same relationship (Allenopithecus nigroviridis, Papio hamadryas, Macaca mulatta, Pygathrix nemaeus, Cercopithecus aethiops)
APES OWM: colobines OWM: cercopithecines NWM
--lysozyme gene sequences; Messier, 1997.
Apes branches indicate human, 2 chimp species, gorilla, orangutan, and gibbon; the two subfamilies of old world monkeys are shown.
--MHC Class II genes; Edwards Genetics 146: 655-668; 1997.
--alpha galactosyltransferase; Galili Proc. Natl. Acad. Sci. 88: 7401-4; 1991.
--h globin ; Koop; Nature 319: 234-7. 1986.
Primates are not the only placental mammals whose genetic sequences suggest that they are related. Not only do dolphins and whales seem to be descended from a common ancestor, they share a common ancestor with the even-toed hoofed mammals (artiodactyls), having evolved from primitive artiodactyl ancestors. Interestingly, the fossil evidence also indicates the whales are descended from artiodactyls.
ARTIODACTYLS, WHALES, AND DOLPHINS
--rRNA sequences; Messenger, 1998. (the five branches on left are artiodactyls; all the remaining branches represent whale and dolphin species)
The combined data of 314 molecular phylogenies indicates that not only do placental mammals include groups which are related to each other through a common ancestry, all placental mammals are descended from a common ancestor (Liu, 2001).
Molecular comparisons indicate that crocodilians are the closest living relatives of birds. The fossil evidence indicates the same relationship: birds and crocodilians are the only surviving archosaurs.
12S and 16S rRNA; Hedges, 1995. (rhea is the branch at the far right of the birds)
Molecular evidence supports that higher vertebrates evolved from amphibians which in turn evolved from sarcopterygian fish. The same pattern is indicated by the fossil record.
Human mice frogs sarcopterygian fish actinopterygian fish
--28S rRNA sequence; Zardoya, 1996. (sturgeon is branch on far right)
The jawless fish are the most basal vertebrates; all other vertebrates are more closely related to each other than any are to jawless fish. (Goodman J Mol Evol 17: 114-20; 1981).
Gnathostome myoglobin with Jawless Fish Hemoglobin
Molecular comparisons indicate that all animals are related by common descent.
Goodman, 1988, Globin
Jawless Fish Mollusc Arthropods Annelids Plants Human
PROTOSTOMES Deuterostome Cnidarians
18S rRNA sequences, Aguinaldo, 1997.
Chordates Echinoderms PROTOSTOMES
--18S rRNA; Lake1990 (chordates are human, frog, lancet, tunicate)
Molecular comparisons indicate that all eukaryotes (animals, fungi, plants, and protists are related).
Elongation Factor 2 (after King, 2001) (Humans first branch on left)
Animals Fungi Protists
a tubulin (after King, 2001)
Animals Fungi Protists Plants Protists
Actin (after King, 2001)
Animals Fungi Protists Plants Protist
MAMMALS BIRDS REPT. AMPH FISH INVERT PLANT FUNGI
--cytochrome c sequence; Fitch
Not only are all eukaryotes related, all living things (eukaryotes and prokaryotes) are related. Of the two groups of prokaryotes, archebacteria and eubacteria, most molecular comparisons indicate that the archebacteria is more closely relate to the eukaryotes.
PHYLOGENY BASED ON ELONGATION FACTOR EF-G/2
ANIMALS FUNGI PLANTS PROTISTS BACTERIA
--amino acid sequences of 57 enzymes; Feng, 1997.
Deuterostomes Protostomes Pseudocoel. Fungi Plants Protists Archebact. Eubact.
--amino acids of 57 enzymes; Doolittle, 1996.
Animals Plants Fungi Protists ARCHAEA EUBACTERIA
Morell, 1997; based on Woese
EUKARYOTES ARCHAEA EUBACTERIA
--rRNA, Pace, 1986. (humans on far left)
IleRS gene sequence; Brown, 1995. (humans far left branch)
EUKARYOTES ARCHAEA EUBACTERIA
In the creationist model, there are groups of living things (which they call “kinds”) which are related by common descent. All kinds however, are equally unrelated to each other. There is no reason that a pattern suggesting a nested hierarchy of relationships should present itself since no group has any special relationship with any other group. Some creationists argue that animals which are superficially similar would naturally be expected to be more similar genetically. There are two main reasons why this argument is inadequate. First of all, the molecules which are used for comparisons are selected because they perform similar functions in the animals being compared (this is actually a requirement for a molecular comparison—if natural selection has acted on a molecule in one lineage differently than in another, the resulting branch patterns will differ from other sequence comparisons). The traits which make humans more superficially similar to apes than to other mammals are not determined by rRNA sequences, alpha hemoglobin sequences, cytochrome c sequences, etc.
Secondly, using such a creationist hypothesis,
one might predict that all monkeys would be most related to each other
molecularly (molecular comparisons do not support this:
Molecular sequence comparisons
overwhelmingly support the nested hierarchy pattern of relationship predicted
in the evolutionary model. Not only is
such a pattern observed, it is the same pattern that is observed in the
analysis of anatomical, embryological, and fossil evidence.