Punctuated equilibrium

Punctuated equilibrium (pl. punctuated equilibria) is a part of evolutionary theory that states that evolution, particularly speciation, occurs relatively quickly with long periods of little change—equilibria—in between. This theory is one of the proposed explanations of the evolutionary patterns of species as observed in the fossil record, particularly the relatively sudden appearance of new species in a geologically short time period, and the perhaps typical lack of substantial change of species during their existence.

Misconceptions

Punctuated equilibrium is often confused with saltationism and catastrophism, and thus mistakenly thought to oppose the concept of gradualism; it is actually more properly understood to be a form of gradualism. This is because even though the changes are considered to be occurring relatively quickly, they are still occurring gradually, with no great changes from one generation to the next. This can be understood by considering an example: Suppose the average length of a limb on a particular species grows 50 centimeters (a large amount) over 70000 years (a geologically short period of time). If the average generation is 7 years, then the given timespan corresponds to 10000 generations. Thus, on average, the limb grows at the minute, gradual rate of only 0.005 cm per generation (= 50 cm / 10000 generations).

Related Topics:
Saltationism - Catastrophism - Gradualism

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The theory is often referred to as an explanation for purported "gaps in the fossil record", i.e. the so-called "missing links". However, this confuses two levels of evolution. It merely explains the small jumps that are observed in fossil lineages within or between closely related fossil species, not the transitions between major categories of organisms. Due to the rarity of preservation and the likelihood that speciation occurs in small populations during geologically short periods of time, transitions between species are uncommon in the fossil record. System approaches can help us to understand more profoundly how a small variation in time can produce a major change to the environment today. However, scientists formed the metasystem transition, where a major change in the metasystem transition may evolve in a very short time period to a higher level of complexity to all living at the time. For example, a single mutation could turn a four-legged creature into a six-legged creature. With the high-levels, mutations are more unlikely to be selected, but throughout time, these high-levels can lead to some revolutionary changes. The changes may be for the better or for the worst in our environment.

Related Topics:
Missing links - Fossil - Species

~ ~ ~ ~ ~ ~ ~ ~ ~ ~