Living fossil

Coelacanths have changed quite a bit since Styloichthys. The claim that they have remained completely unchanged is simply untrue.

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A living Lingula that's actually similar to its ancestors 450 million years ago.

A living fossil is a species (or sometimes a higher group) that has an extensive fossil record but also retains known living specimens. Creationists love them as they believe that such things appear to deny evolution, not realising that morphological adaptations are not selected in a stable environment. Living fossils are sometimes Lazarus taxa, i.e. they disappear from the fossil record and are presumed extinct but are later found alive.

Selected examples

• The coelacanth is said to be a living fossil that has not changed at all between its fossil form and the living fish we know today, but this is a wildly inaccurate assessment. The most common misconception about the coelacanth is that the living Latimeria is of the same sort as the Palaeozoic and Mesozoic coelacanth. Although it is related to an order of much smaller fish from millions of years ago, coelacanths make up an entire order (Coelacanthiformes) of which the Latimeria is the sole living survivor. (By comparison, the order that humans belong to is the primates, so claiming coelacanths haven't changed in all those years is like claiming that humans are identical to early monkeys.) The gap throughout the Cenozoic is because the coelacanth's current habitat is in deep water, where fossilisation rarely happens.
• The dawn redwood Metasequoia was thought to be extinct, until a grove of them was found in China in the mid-20th century. It is related to similar species that lived until about 5 million years ago.
• One sort of brachiopod, the Lingula, has a fossil record extending to the Ordovician, with close relatives going all the way to the Cambrian.
• The horseshoe crab, virtually unchanged in 250 million years. Or perhaps not, what with Austrolimulus looking more like the head of a trident than a modern horseshoe crab.

History of term

Charles Darwin coined the term "living fossil" in The Origin of Species. In reference to several genera of fresh water fish, he noted:

These anomalous forms may almost be called living fossils; they have endured to the present day, from having inhabited a confined area, and from having thus been exposed to less severe competition.

Note that Darwin also provides an explanation as to why living fossils do not contradict the tenets of evolution.

Since then, creationists have latched onto living fossils, believing they provide evidence against evolution. Harun Yahya explains it:

Countless living things have remained unchanged for millions of years, and their current anatomical structures are exactly the same as they were millions of years ago. The fossil record is almost complete with both animal and plant specimens demonstrating this. It definitively and scientifically refutes evolution.

This claim fails to recognise that, although evolution predicts that species can change, it does not require that species must change. This is due in part to a misunderstanding of how evolution resulted in the development of new species. Yahya further explains:

According to the theory, all living things have descended from various "ancestral" forms. A living species that existed before gradually turned into another species, and every present species emerged in this way. According to the theory, this transition took place slowly over hundreds of millions of years and progressed in stages. That being the case, countless numbers of "intermediate forms" must have emerged and lived over the long process of transition in question.

This interpretation assumes that the tempo of evolution is gradual and steady. Contrary to this assumption, the mode of evolution proposed by Darwin, while incremental, is not equivalent to phyletic gradualism. Thus it is unlikely that diversification took place because one species "gradually turned into another species." As indicated by the fossil evidence, most new species probably developed by rapidly branching from ancestral species followed by long periods of evolutionary stasis.

Today, the mechanism is known: when selection pressure is lessened, or favors traits the organism already possesses to be successful in the current niche, stabilizing selection occurs, which favors the existing, successful body plan; stabilizing selection is the opposite of disruptive selection.

Some living fossils like lungfish can be problematic for creationists.

Elvis taxon

An Elvis taxon is a species or higher group that has been misidentified as reappearing after presumed extinction. These examples may appear to have some similarities with older and/or extinct species—but unlike other living fossils are not actual descendants of them. The similarities are just coincidental, most likely due to convergent evolution, making the Elvis taxon polyphyletic with its extinct "ancestor".

The term comes from Elvis Presley, and references the countless Elvis impersonators that have cropped up since his death. They may look like Elvis, but they're not actually related to him.

Zombie taxon

A related phenomenon, a zombie taxon is a reworked fossil that was washed out of the original rocks and re-deposited in later sediments. The name is a play on the fact that the fossil moved after the animals death kinda like a zombie.

Lazarus taxon

A Lazarus taxon (plural taxa) is a taxon that disappears for one or more periods from the fossil record, only to appear again later (either later in the fossil record or alive today). The term is exclusively used to refer to gaps in the fossil record wherein the taxon is believed to have become extinct at one point only to be found in later strata afterwards. The term refers to the story in the Christian biblical Gospel of John, in which Jesus Christ raised Lazarus from the dead. The gap between the Lazarus taxon and the last previous known member is referred to as a ghost lineage, although the term ghost lineage can refer to any gap in the record.

The coelacanth is an example of a Lazarus taxon. The longest ghost lineage is the Monoplacophora, a class of molluscs that were originally believed to have become extinct 388 million years ago before living members were described from deep waters of Costa Rica in 1952 with Pleistocene fossils being recovered in the late 80s early 90s.

See also

• Fossil
• How come there are still monkeys?
• Linnaean taxonomy
• Punctuated equilibrium
• Cryptozoology — most of which are completely fake, but a few of which are for alleged sightings of extinct animals: Basilosaurus, Gigantopithecus, and thylacine

External links

• Neyman, Greg (April 13, 2005). "Creation Science Rebuttals: Living Fossils." Answers in Creation.
• Living Fossil on CreationWiki
• Morris, Henry. "The Profusion of Living Fossils." Institute for Creation Research. (suggests dinosaurs were living fossils "called dragons")