Even though creationists are uneducated morons they should be able to understand this undeniable evidence for evolution.

Wikipedia - Atavism:

In biology, an atavism is a modification of a biological structure whereby an ancestral trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways; one of which is when genes for previously existing phenotypic features are preserved in DNA, and these become expressed through a mutation that either knocks out the overriding genes for the new traits or makes the old traits override the new one. A number of traits can vary as a result of shortening of the fetal development of a trait (neoteny) or by prolongation of the same. In such a case, a shift in the time a trait is allowed to develop before it is fixed can bring forth an ancestral phenotype. Atavisms are often seen as evidence of evolution.

Evolutionarily traits that have disappeared phenotypically do not necessarily disappear from an organism's DNA. The gene sequence often remains, but is inactive. Such an unused gene may remain in the genome for many generations. As long as the gene remains intact, a fault in the genetic control suppressing the gene can lead to it being expressed again. Sometimes, the expression of dormant genes can be induced by artificial stimulation.

Atavisms have been observed in humans, such as with infants born with vestigial tails (called a "coccygeal process", "coccygeal projection", or "caudal appendage"). Atavism can also be seen in humans who possess large teeth, like those of other primates. In addition, a case of "snake heart", the presence of "coronary circulation and myocardial architecture [which resemble] those of the reptilian heart", has also been reported in medical literature.

Other examples of observed atavisms include:

Hind limbs in whales.

Reappearance of limbs in limbless vertebrates.

Back pair of flippers on a bottlenose dolphin.

Extra toes of the modern horse.

Re-evolution of sexuality from parthenogenesis in orbitid mites.

Teeth in chickens.

Dewclaws in dogs.

Reappearance of wings on wingless stick insects and earwigs.

Atavistic muscles in several birds and mammals such as the beagle and the jerboa.

Extra toes in guinea pigs.

Reemergence of sexual reproduction in the flowering plant Hieracium pilosella and the Crotoniidae family of mites.

Webbed feet in adult axolotls.

Human tails (not pseudo-tails) and supernumerary nipples in humans (and other primates).

Color blindness in humans.

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"We've already learned that some species of whales retain vestigal pelvises and rear leg bones, but about one whale in five hundred is actually born with a rear leg that protrudes outside the body wall. These limbs show all degrees of refinement, with many of them clearly containing the major leg bones of terrestrial animals--the femur, tibia, and fibula. Some even have feet and toes!"

-- "Why Evolution is True" by Jerry Coyne

Early embryos of various species display some ancestral features, like the tail on this human fetus. These features normally disappear in later development, but it may not happen if the animal has an atavism.