Evolution. One thing does NOT turn into another!


This is in response to a few rather absurd notes i received in response to a prior blog.

Dogs will always be dogs no matter how much cross breeding or selective breeding humans put them through.

Very true.

Just like Epihippus who lived 47 million years ago was as much a horse as thoroughbreds racing around tracks today. 


Do we see Epihippus walking around?   No we do not.  Because the habitat changed and Epihippus changed.  Over time he got bigger, he got stronger teeth, more specialized at eating grass instead of leaves…his middle toe got stronger as he learned to walk on it more and eventually his other toes weren’t used as much…they grew weaker and one day horses just didn’t have any extra toes anymore–just the hard crusty nail (or chestnut) we can still find half-way up modern horses cannon bones today.

What some Creationists with blinders don’t get, and don’t want to get.  Humans did not come from apes.  We are simply of the same family as apes. Because there are still apes around today just as there are humans around today. Does one sibling become another? They are our siblings…our cousins. The most similar to us genetically. We are the same with them (primates) like lions and tigers are the same (felines). WE were never THEM. They never morphed into us.

I understood this concept even when I was a Christian…a child! Being a Christian should not excuse being ignorant. How difficult is this concept really???

Are there Epihippus still around today?  No, because between Epihippus and the modern day horse there was a series of horses adapting from a creature about the size of a fox to a creature approx 14 hands tall, or the size of a large modern day pony.  These later forms of horse replaced the earlier forms because the earlier forms died out–were not able to continue to live in their changing environment.  So today we see the horse, but we do not see the earlier forms of HORSE that were replaced.

This same thing happened with human beings.  Apes did not become humans.  Apes are still here and have been here for a very long time.  There were other species of primates (which humans are) that are not walking around now because they too adapted to their changing environment and changed and replaced the earlier versions no longer able to survive.  Our ancestors have long since disappeared from the earth, just as the apes ancestors have long since disappeared from the earth.  We are all primates however, so a very long time ago, apes and humans did have the same ancestor.  We are cousins to apes.  We are apes ourselves of a different kind, classified as great apes, actually.  but we are not gorillas like we see gorillas today.  We are not chimpanzees either.   We are human beings.  We have always been human beings and we will always be human beings.

I really wish Creationists would get it.

Another modern day example of evolution:   records–vinyl–45’s, etc….then 8 track tape players…then reel to reel players…then cassette players…then CD players…then DVD players…then digital.   Do we still see 8 track tape players around today?  Do we see very many cassette players around today?  Did these things suddenly turn into something else?  Or were they REPLACED by a newer better more adaptable technology?  This too is evolution in the modern world.  There are lots of examples of evolution at work all around us.  But where are there any examples of Creationism in the modern world?  There are none.

Copied from Wikipedia:

Epihippus

In the mid-Eocene, about 47 million years ago, Epihippus, a genus which continued the evolutionary trend of increasingly efficient grinding teeth, evolved from Orohippus. Epihippus had five grinding, low-crowned cheek teeth with well-formed crests. A late species of Epihippus, sometimes referred to as Duchesnehippus intermedius, had teeth similar to Oligocene equids, although slightly less developed. Whether Duchesnehippus was a subgenus of Epihippus or a distinct genus is disputed.[citation needed]

Mesohippus

In the late Eocene and the early stages of the Oligocene epoch (32–24 mya), the climate of North America became drier, and the earliest grasses began to evolve. The forests were yielding to flatlands,[citation needed] home to grasses and various kinds of brush. In a few areas, these plains were covered in sand,[citation needed] creating the type of environment resembling the present-day prairies.

In response to the changing environment, the then-living species of Equidae also began to change. In the late Eocene, they began developing tougher teeth and becoming slightly larger and leggier, allowing for faster running speeds in open areas, and thus for evading predators in nonwooded areas[citation needed]. About 40 mya, Mesohippus (“middle horse”) suddenly developed in response to strong new selective pressures to adapt, beginning with the species Mesohippus celer and soon followed by Mesohippus westoni.

In the early Oligocene, Mesohippus was one of the more widespread mammals in North America. It walked on three toes on each of its front and hind feet (the first and fifth toes remained, but were small and not used in walking). The third toe was stronger than the outer ones, and thus more weighted; the fourth front toe was diminished to a vestigial nub. Judging by its longer and slimmer limbs, Mesohippus was an agile animal.

Mesohippus was slightly larger than Epihippus, about 610 mm (24″) at the shoulder. Its back was less arched, and its face, snout, and neck were somewhat longer. It had significantly larger cerebral hemispheres, and had a small, shallow depression on its skull called a fossa, which in modern horses is quite detailed. The fossa serves as a useful marker for identifying an equine fossil’s species. Mesohippus had six grinding “cheek teeth”, with a single premolar in front—a trait all descendant Equidae would retain. Mesohippus also had the sharp tooth crests of Epihippus, improving its ability to grind down tough vegetation.

[edit] Miohippus

Around 36 million years ago, soon after the development of Mesohippus, Miohippus (“lesser horse”) emerged, the earliest species being Miohippus assiniboiensis. Like Mesohippus, Miohippus‘s evolution was relatively abrupt, though a few transitional fossils linking the two genera have been found. Mesohippus was once believed to have anagenetically evolved into Miohippus by a gradual series of progressions, but new evidence has shown its evolution was cladogenetic: a Miohippus population split off from the main Mesohippus genus, coexisted with Mesohippus for around four million years, and then over time came to replace Mesohippus.[16]

Miohippus was significantly larger than its predecessors, and its ankle joints had subtly changed. Its facial fossa was larger and deeper, and it also began to show a variable extra crest in its upper cheek teeth, a trait that became a characteristic feature of equine teeth.

Miohippus ushered in a major new period of diversification in Equidae.[14] While Mesohippus died out in the mid-Oligocene, Miohippus continued to thrive, and in the early Miocene (24–5.3 mya), it began to rapidly diversify and speciate. It branched out into two major groups, one of which adjusted to the life in forests once again, while the other remained suited to life on the prairies.[citation needed]

[edit] Miocene and Pliocene: true equines

[edit] Kalobatippus

The forest-suited form was Kalobatippus (or Miohippus intermedius, depending on whether it was a new genus or species), whose second and fourth front toes were long, well-suited travel on the soft forest floors. Kalobatippus probably gave rise to Anchitherium, which travelled to Asia via the Bering Strait land bridge, and from there to Europe.[17] In both North America and Eurasia, larger-bodied genera evolved from Anchitherium: Sinohippus in Eurasia and Hypohippus and Megahippus in North America.[18] Hypohippus became extinct by the late Miocene.[19]

[edit] Parahippus

The Miohippus population that remained on the steppes is believed to be ancestral to Parahippus, a North American animal about the size of a small pony, with a prolonged skull and a facial structure resembling the horses of today. Its third toe was stronger and larger, and carried the main weight of the body. Its four premolars resembled the molar teeth and the first were small and almost nonexistent. The incisive teeth of Parahippus, like those of its predecessors, had a crown as humans do; however, the top incisors had a trace of a shallow crease marking the beginning of the core/cup.

[edit] Merychippus

Merychippus, an effective grazer and runner

In the middle of the Miocene epoch, the grazer Merychippus flourished. It had wider molars than its predecessors, which are believed to have been used for crunching the hard grasses of the steppes. The hind legs, which were relatively short, had side toes equipped with small hooves, but they probably only touched the ground when running.[14] Merychippus radiated into at least 19 additional grassland species.

[edit] Hipparion

Protohippus simus

Three lineages within Equidae are believed to be descended from the numerous varieties of Merychippus: Hipparion, Protohippus and Pliohippus. The most different from Merychippus was Hipparion, mainly in the structure of tooth enamel: in comparison with other Equidae, the inside, or tongue side, had a completely isolated parapet. A complete and well-preserved skeleton of the North American Hipparion shows an animal the size of a small pony. They were very slim, rather like antelopes, and were adapted to life on dry prairies. On its slim legs, Hipparion had three toes equipped with small hooves, but the side toes did not touch the ground.

In North America, Hipparion and its relatives (Cormohipparion, Nannippus, Neohipparion, and Pseudhipparion), proliferated into many kinds of equids, at least one of which managed to migrate to Asia and Europe during the Miocene epoch.[20] (European Hipparion differs from American Hipparion in its smaller body size – the best-known discovery of these fossils was near Athens.)

[edit] Pliohippus

Pliohippus pernix

Pliohippus arose from Callippus in the middle Miocene, around 12 mya. It was very similar in appearance to Equus, though it had two long extra toes on both sides of the hoof, externally barely visible as callused stubs. The long and slim limbs of Pliohippus reveal a quick-footed steppe animal.

Until recently, Pliohippus was believed to be the ancestor of present-day horses because of its many anatomical similarities. However, though Pliohippus was clearly a close relative of Equus, its skull had deep facial fossae, whereas Equus had no fossae at all. Additionally, its teeth were strongly curved, unlike the very straight teeth of modern horses. Consequently, it is unlikely to be the ancestor of the modern horse; instead, it is a likely candidate for the ancestor of Astrohippus.[21]

[edit] Dinohippus

Dinohippus was the most common species of Equidae in North America during the late Pliocene. It was originally thought to be monodactyl, but a 1981 fossil find in Nebraska shows some were tridactyl.

[edit] Plesippus

Mounted skeleton of Hagerman horse (Equus simplicidens)

Plesippus is often considered an intermediate stage between Dinohippus and the extant genus, Equus.

The famous fossils found near Hagerman, Idaho were originally thought to be a part of the genus Plesippus. Hagerman Fossil Beds (Idaho) is a Pliocene site, dating to about 3.5 mya. The fossilized remains were originally called Plesippus shoshonensis, but further study by paleontologists determined the fossils represented the oldest remains of the genus Equus.[22] Their estimated average weight was 425 kg, roughly the size of an Arabian horse.

At the end of the Pliocene, the climate in North America began to cool significantly and most of the animals were forced to move south. One population of Plesippus moved across the Bering land bridge into Eurasia around 2.5 mya.[23]

[edit] Modern horses

[edit] Equus

Skull of a giant extinct horse of the genus Equus, E. eisenmannae

The genus Equus, which includes all extant equines, is believed to have evolved from Dinohippus, via the intermediate form Plesippus. One of the oldest species is Equus simplicidens, described as zebra-like with a donkey-shaped head. The oldest material to date is ~3.5 million years old from Idaho, USA. The genus appears to have spread quickly into the Old World, with the similarly aged Equus livenzovensis documented from western Europe and Russia.[24]

Molecular phylogenies indicate the most recent common ancestor of all modern equids (members of the genus Equus) lived ~5.6 (3.9-7.8) mya. The oldest divergencies are the Asian hemiones (subgenus E. (Asinus)), including the kulan, onager, and kiang), followed by the African zebras (subgenera E. (Dolichohippus), and E. (Hippotigris)). All other modern forms including the domesticated horse (and many fossil Pliocene and Pleistocene forms) belong to the subgenus E. (Equus) which diverged ~4.8 (3.2-6.5) million years ago.[25]

Pleistocene horse fossils have been assigned to a multitude of species, with over 50 species of equines described from the Pleistocene of North America alone, although the taxonomic validity of most of these has been called into question.[26] Recent genetic work on fossils has found evidence for only three genetically divergent equid lineages in Pleistocene North and South America.[25] These results suggest all North American fossils of caballine-type horses (which also include the domesticated horse and Przewalski’s horse of Europe and Asia), as well as South American fossils traditionally placed in the subgenus E. (Amerhippus)[27] belong to the same species: E. ferus. Remains attributed to a variety of species and lumped as New World stilt-legged horses (including E. francisci, E. tau, E. quinni and potentially North American Pleistocene fossils previously attributed to E. cf. hemiones, and E. (Asinus) cf. kiang) likely all belong to a second species endemic to North America, which despite a superficial resemblance to species in the subgenus E. (Asinus) (and hence occasionally referred to as North American ass) is closely related to E. ferus.[25] Surprisingly, the third species, endemic to South America, and traditionally referred to as Hippidion, originally believed to be descended from Pliohippus, was shown to be a third species in the genus Equus, closely related to the New World stilt-legged horse.[25] The temporal and regional variation in body size and morphological features within each lineage indicates extraordinary intraspecific plasticity. Such environment-driven adaptative changes would explain why the taxonomic diversity of Pleistocene equids has been overestimated on morphoanatomical grounds.[27]

According to these results, it appears the genus Equus evolved from a Dinohippus-like ancestor ~4-7 mya. It rapidly spread into the Old World and there diversified into the various species of asses and zebras. A North American lineage of the subgenus E. (Equus) evolved into the New World stilt-legged horse (NWSLH). Subsequently, populations of this species entered South America as part of the Great American Interchange shortly after the formation of the Isthmus of Panama, and evolved into the form currently referred to as “Hippidion” ~2.5 million years ago. Hippidion is thus unrelated to the morphologically similar Pliohippus, which presumably went extinct during the Miocene. Both the NWSLH and Hippidium show adaptations to dry, barren ground, whereas the shortened legs of Hippidion may have been a response to sloped terrain.[27] In contrast, the geographic origin of the closely related modern E. ferus is not resolved. However, genetic results on extant and fossil material of Pleistocene age indicate two clades, potentially subspecies, one of which had a holarctic distribution spanning from Europe through Asia and across North America and would become the founding stock of the modern domesticated horse.[28][29] The other population appears to have been restricted to North America. One or more North American populations of E. ferus entered South America ~1.0-1.5 million years ago, leading to the forms currently known as “E. (Amerhippus)“, which represent an extinct geographic variant or race of E. ferus, however.

[edit] Pleistocene extinctions

Digs in western Canada have unearthed clear evidence horses existed in North America until about 12,000 years ago.[30] However, all Equidae in North America ultimately became extinct. The causes of this extinction (simultaneous with the extinctions of a variety of other American megafauna) have been a matter of debate. Given the suddenness of the event and because these mammals had been flourishing for millions of years previously, something quite unusual must have happened. The first main hypothesis attributes extinction to climate change. For example, in Alaska, beginning approximately 12,500 years ago, the grasses characteristic of a steppe ecosystem gave way to shrub tundra, which was covered with unpalatable plants.[31][32] The other hypothesis suggests extinction was linked to overexploitation of naive prey by newly arrived humans. The extinctions were roughly simultaneous with the end of the most recent glacial advance and the appearance of the big game-hunting Clovis culture.[33][34] Several studies have indicated humans probably arrived in Alaska at the same time or shortly before the local extinction of horses.[34][35][36] Additionally, it has been proposed that the steppe-tundra vegetation transition in Beringia may have been a consequence, rather than a cause, of the extinction of megafaunal grazers.[37]

In Eurasia, horse fossils began occurring frequently again in archaeological sites in Kazakhstan and the southern Ukraine about 6,000 years ago.[28] From then on, domesticated horses, as well as the knowledge of capturing, taming, and rearing horses, probably spread relatively quickly, with wild mares from several wild populations being incorporated en route.[29]

[edit] Return to the Americas

Horses only returned to the Americas with Christopher Columbus in 1493. These were Iberian horses first brought to Hispaniola and later to Panama, Mexico, Brazil, Peru, Argentina, and, in 1538, Florida.[38] The first horses to return to the main continent were 16 specifically identified horses brought by Hernan Cortes. Subsequent explorers, such as Coronado and De Soto brought ever-larger numbers, some from Spain and other from breeding establishments set up by the Spanish in the Caribbean. Later, as Spanish missions were founded on the mainland, horses would eventually be lost or stolen, and proliferated into large herds of feral horses that became known as mustangs.[citation needed]

The indigenous peoples of the Americas did not have a specific word for horses, and came to refer to them in various languages as a type of dog or deer (in one case, “elk-dog”).[citation needed]

[edit] Details

[edit] Toes

The ancestors of the horse came to walk only on the end of the third toe and both side toes. Skeletal remnants show obvious wear on the back of both sides of metacarpal and metatarsal bones, commonly called the “splint bones”. They are the remnants of the second and the fourth toe. Modern horses retain the splint bones; they are often believed to be useless attachments, but they in fact play an important role in supporting the carpal joints (front knees) and even the tarsal joints (hocks).

[edit] Teeth

Throughout the phylogenetic development, the teeth of the horse underwent significant changes. The type of the original omnivorous teeth with short, “bumpy” molars, with which the prime members of the evolutionary line distinguished themselves, gradually changed into the teeth common to herbivorous mammals. They became long (as much as 100 mm), roughly cubical molars equipped with flat grinding surfaces. In conjunction with the teeth, during the horse’s evolution, the elongation of the facial part of the skull is apparent, and can also be observed in the backward-set eyeholes. In addition, the relatively short neck of the equine ancestors became longer, with equal elongation of the legs. Finally, the size of the body grew as well.

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