How is it possible for Modern man to evolve from Eukaryotic Cells in only 7500 speciations when it took 11,500 to go from single cell to Eukaryotic Cells?
Not all Eukaryotic Cells life is multi-cellular. Eukaryotic Cells first evolved as single cell life forms, about 2 billion years ago (although it can be - and is - argued that this was developed by one cell being absorbed inside another to create a new kind of single cell). Then it only took 0.5 billion years to form the first mutlicellular life.
But why is this (change over time) a problem? Look at those Eukaryotic Cells and see if there is any substantial difference between them: what is inside a single cell life cell is inside the multi-cell life cell. The change from original cell form to Eukaryotic Cells is actually much more significant, as this adds several features to make these "modern" cells.
Think of the time it takes a child to learn to stack one block on top of another, and then the time needed to make a stack 3, 4, 5 blocks high. All multicellular life develops from single cells, it's just a matter of stacking the cells up to make a multicellular life.
What you really need to look at is the formation of the basic body plan of an interactive multicellular life as opposed to one that is a group of similar function cells. Once you have a basic body plan then all you need is variations on a theme.
That leaves 7500 speciations to get to modern man, from Eukaryotic Cells.
Don't confuse the existence of man with the need for man to be a result. Functionally man is no different than the first mammal, which is functionally no different than the first reptile, which is ... etc.
And don't confuse a minimum with average or expect evidence from one example to apply to others: the evidence from the forams only applies to the forams that stayed forams (the data group of the study), so there could be undocumented speciation events where forams became no-longer-forams (perhaps they ditched their shells eh?).
We also do not have any figures for speciation rates when sexual selection is a factor. The evidence from human history is that this can significantly alter the rate of mutation selection -- just the difference in fixed genes between man and chimps shows this.
The more you break the development over time scale down the more you will see that only small steps are needed.
quote:Through dating analysis, he and his colleague showed that the forams could produce a whole new species in as little as 200,000 years--speedy by Darwinian standards. "But as fast as this is, it's still far too slow to be classed as punctuational," says Arnold.
If they could have provided a detailed trail with the formas forking off and becoming some other family of creature they would have been heros.
Why? There is plenty of evidence for this happening, so it would not add anything new to the concept of evolution or the evidence for it.
The foraminifera are also an order not just a species, so there are changes at the family level too (between species and order).
If you want an example of species evolving into a substantially different species try horses. Part of this depends on what you think is distinctive enough of a difference ...
abe: this is copied from another thread that is not open to general discussion.
We can talk about horses and the distinctive development of the modern horse and single-toe hoof from the splayed toed dog sized "eohippus":
quote:Look at how the bones in horse feet have changed over time. They became longer and more streamlined, enabling horses to run faster to avoid predators.
Check the above link to see images of the legs of four different horse ancestors. You can see a splayed toe stance for Hyracotherium and Miohippus but a single toe stance in Merychippus and Equus.
quote:Eohippus was a descendent of the Condylarth, a dog-sized, five-toed creature that lived about 75 million years ago. It lived during the early Eocene period, which took place 50 to 60 million years ago. Eohippus, which means "dawn horse," stood about twelve to fourteen inches at the shoulder and weighed about twelve pounds. It looked nothing like a horse. It had an arched back, short neck, short snout, short legs, and a long tail. Its color probably most resembled that of a deer, a darker background with lighter spots. The legs of Eohippus were flexible and rotating with all major bones present and unfused. It had a choppy, up-down gait and was not very fast. There were four toes on each front foot and three toes on the hind. The vestigial toes - two on the front feet and one on the hind - were still present.
It had a small brain and low-crowned teeth with three incisors, one canine, four distinct premolars, and three "grinding" molars in each side of each jaw. Browsing on fruit and fairly soft foliage, Eohippus probably lived in an environment with soft soil, the kind found on jungle floors and around the edges of pools. Since Eohippus walked on the pads of its feet, it was able to cross wet, marshy ground without much difficulty.
The coloration is pure speculation, of course, but the size and stance are based on the physiology of the skeleton. Now lets also look at the Condylarth:
quote:Back in the northern hemisphere, another family of condylarths, the Phenacodontidae, may include the ancestors of a more familiar ungulate order: The odd-toed ungulates or Perissodactyla, represented by horses, rhinos and tapirs in the recent fauna. Historically, phenacodontids form the core of the Condylarthra. Well-preserved skeletons are known for the type genus Phenacodus, which is a good model of an ancestral ungulate with beginning adaptations for running. Unlike arctocyonids, periptychids or mioclaenids, the phenacodontids are not part of the first wave of condylarths that populated North America. They first appear with the fox-sized Tetraclaenodon in the middle Paleocene of that continent. The appearance of the more advanced phenacodontids Phenacodus and Ectocion marks the beginning of late Paleocene time in North America. The type genus Phenacodus covers the large size range of phenacodontids and includes roughly sheep-sized animals. Members of the genus Ectocion were usually smaller, with a body mass of only 3 kg in the smallest species, but there is some overlap in size between the two genera. Phenacodontids were the dominant mammals in the latest Paleocene of North America and account for up to 50% of all mammal specimens in faunas of that age.
Figure 5: Reconstruction of the late Paleocene to middle Eocene Phenacodus, a sheep-sized herbivore with improved capabilities for running. From Savage & Long (1986).
This is the most "horse-like" image from this site, and it looks much more like a dog than a horse eh? Of course the coloration and fur are speculation, but the size and stance are again based on the physiology of the skeleton.
To see what the skeletons looked like for the four species used for the leg examples at the start we go to:
(NOTE: LINKS INTENTIONALLY BROKEN - this image is copied from the original to save bandwidth, go to the original Stratmap for the links to work).
(Hyracotherium)- This small dog-sized animal represents the oldest known horse. It had a primitive short face, with eye sockets in the middle and a short diastema (the space between the front teeth and the cheek teeth).
Although it has low-crowned teeth, we see the beginnings of the characteristic horse-like ridges on the molars.
Hyracotherium is better known as "eohippus" - which means "the dawn horse." The name also refers to the fact that it lived during the Eocene.
(Miohippus) - Species of Miohippus gave rise to the first burst of diversity in the horse family. Until Miohippus, there were few side branches, but the descendants of Miohippus were numerous and distinct. During the Miocene, over a dozen genera existed.
Fossils of Miohippus are found at many Oligocene localities in the Great Plains, the western US and a few places in Florida. Species in this genus lived from about 32-25 million years ago.
(Merychippus) - Merychippus represents a milestone in the evolution of horses. Though it retained the primitive character of 3 toes, it looked like a modern horse. Merychippus had a long face. Its long legs allowed it to escape from predators and migrate long distances to feed. It had high-crowned cheek teeth, making it the first known grazing horse and the ancestor of all later horse lineages.
Fossils of Merychippus are found at many late Miocene localities throughout the United States. Species in this genus lived from 17 - 11 million years ago
(Equus) - Equus is the only surviving genus in the once diverse family of horses. Domesticated about 3,000 years ago, the horse had a profound impact on human history in areas such as migration, farming, warfare, sport, communication and travel.
Species of Equus lived from 5 million years ago until the present. Living species include horses, asses, and zebras. Fossils of Equus are found on every continent except Australia and Antarctica.
I selected the same species as were listed for the legs above for convenience here - on the original link you select by clicking on the skulls.
So we have a sequence of species that starts with one standing on the fleshy pads of several splayed toes to the modern species that stands not just on one toe but on the toe-nail of that single toe. But that is not all:
quote:A horse's hoof is composed of the wall, sole and frog. The wall is simply that part of the hoof that is visible when the horse is standing. It covers the front and sides of the third phalanx, or coffin bone. The wall is made up of the toe (front), quarters (sides) and heel.
The wall of the hoof is composed of a horny material that is produced continuously and must be worn off or trimmed off. The hoof wall does not contain blood vessels or nerves. In the front feet, the wall is thickest at the toe; in the hind feet the hoof wall is of a more uniform thickness. The wall, bars and frog are the weight-bearing structures of the foot. Normally the sole does not contact the ground.
As weight is placed on the hoof, pressure is transmitted through the phalanges to the wall and onto the digital cushion and frog. The frog, a highly elastic wedge-shaped mass, normally makes contact with the ground first. The frog presses up on the digital cushion, which flattens and is forced outward against the lateral cartilages. The frog also is flattened and tends to push the bars of the wall apart (Figure 3). When the foot is lifted, the frog and other flexible structures of the foot return to their original position.
When the foot is placed on the ground, blood is forced from the foot to the leg by the increase in pressure and by the change in shape of the digital cushion and the frog. The pressure and the change in shape compress the veins in the foot. When the foot is lifted, the compression is relieved and blood flows into the veins again. In this way, the movement of these structures in the hoof acts as a pump.
This is much more difference in a feature than "just an increase in length" (as in an elephants trunk), it is a totally different structure to stand on (eohippus stood on his toes pads, equus stands on a hoof which not only is not a toe pad, but a feature that wasn't present in the eohippus) and it incorporates a new {added\changed} structure to increase blood flow by acting as a secondary pump.
Not only that the effect of changing the foot structure from a flat footed splayed toed eohippus to the single toed equus also involves standing the foot up on the tip of the toe and using each of the bones between the tip and the heel to effectively make the leg longer for faster running while also making it more flexible than just adding length to the bones of the leg. Probably useful for getting through tight spots and to keep from tripping ... it certainly helps horses jumping in shows from hitting that top bar.
Totally different foot structure, coupled with totally different leg structure (with some ex toe bones now effectively used as leg bones).
The question again is how much change is enough? Try walking around the house on the tip of one toe, then compare your foot to that of eohippus.
Enjoy.
References:
Anonymous, "Evolution of the Horse: Eohippus" Sarah's Horse Farm, Updated 10 Aug 2000, Accessed 12 Jan, 2007
Anonymous, "Fossil Horse Cybermuseum" The Florida Museum of Natural History, Updated 8 Jan 2007, Accessed 12 Jan, 2007
Jehle, Martin, "Condylarths: Archaic hoofed mammals" Paleocene mammals of the world, Updated ?, Accessed 12 Jan, 2007
McClure, Robert C. et al "Functional Anatomy of the Horse Foot" Department of Veterinary Anatomy, College of Veterinary Medicine, Updated 10 May 2006, Accessed 12 Jan, 2007
This a contentious issue, some people argue that plants can have sexual selection, so I can't imagine they would except Foraminifers.
True. And one could argue that sexual selection also goes on in mosquitoes and the like via variations in the sexual organs\fit.
Perhaps what I mean is conscious\unconscious selection - based on some mental perception.
So the question is where does run-away sexual selection fit on the conscious\unconscious scheme of things? This would represent the fast-tracked selection process that, imh(ysa)o, would show a faster than normal rate of fixing selected mutations.
quote:Equus is the only surviving genus in the once diverse family of horses.
Living species include horses, asses, and zebras. Fossils of Equus are found on every continent except Australia and Antarctica.
And there are extinct species within Equus. One within modern times (recorded history). Not all genera represented by multiple species (eg - man) but most are (else why create a different genus? It's an arbitrary distinction).
It does not appear that the horse went very fast.
When you include the species within the genus categories then it does appear that horse was faster than shown here, though the chart isn't detailed to the species level (the way foraminifera were, nor is the foraminifera data broken down by genera).
It does not appear that horse ancestors engaged in the type of run-away sexual selection for specific traits that I was talking about either -- there is no sexual dimorphism beyond a slight difference in size (and that is due to dominant male herding behavior) -- and no "peacock tail" features. When we look at man we do see sexual dimorphism and "peacock tail" features: bare-appearing skin, long head hair, large creative brain, large sexual organs, and the like -- more extreme than in any other ape or primate, and some (bare skin, long hair, large brain) extreme to the point of threatening survival of those with the features. This to me is a significant element of human evolution since the common ancestor with chimps.
The question remains with only 7500 levels how did modern man evolve from the Eukaryotic Cells.
The Abbott and Costello (and 3 stooges, and other vaudeville acts) way
quote:(A) Pan troglodytes, chimpanzee, modern (B) Australopithecus africanus, STS 5, 2.6 My (C) Australopithecus africanus, STS 71, 2.5 My (D) Homo habilis, KNM-ER 1813, 1.9 My (E) Homo habilis, OH24, 1.8 My (F) Homo rudolfensis, KNM-ER 1470, 1.8 My (G) Homo erectus, Dmanisi cranium D2700, 1.75 My (H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My (I) Homo heidelbergensis, "Rhodesia man," 300,000 - 125,000 y (J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y (K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y (L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y (M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y (N) Homo sapiens sapiens, modern
One species of forams remained the same for 500,000 years.
While chimps go from ~B to A (thus demonstrating that large changes are not necessary over time and that rates are different in different species under different selection pressures).
Like I said that is too much to swallow.
Your problem, not necessary for those that look at the evidence.
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