Posted on 10/07/2007 10:11:11 AM PDT by truthfinder9
Many people are convinced that human evolution is a fact. Often they will cite the existence of hominids in the fossil record as evidence for their conviction. These creatures presumably represent evolutionary intermediates between an ape-like creature and modern humans.
The standard evolutionary model for human origins views Homo habilis as the first member of our genus (Homo). This hominid initially appears in the fossil record about 2.6 million years ago (mya) and seemingly gives rise directly to Homo erectus around 1.9 mya.
The direct transformation of H. habilis into H. erectus appeared to gain support from the recovery of hominid remains from Dmanisi, Georgia, in 1999 and 2001. Dating at about 1.8 million years in age, these hominids appear to be intermediate in morphology between H. habilis and H. erectus.
The recent analysis of H. habilis and H. erectus fossils recovered near Lake Turkana, Kenya, in 2000 muddies the place of H. habilis in human evolutionary scenarios and widens the gap between H. erectus and modern humans. The fossil specimens consisted of a faceless H. erectus skull, dated at 1.55 million years in age, and a H. habilis jawbone dated to be 1.44 million years old. Paleoanthropologists find each of these fossils surprising for different reasons.
The 1.44 million-year-old date for H. habilis means that this hominid must have coexisted with H. erectus. This finding contradicts the standard model. If H. habilis gave way to H. erectus it should not have coexisted with this hominid. The fossils indicate that H. habilis and H. erectus were morphologically distinct species that exploited different ecological niches within the same geographical region, reinforcing the conclusion that H. habilis didn’t directly transform into H. erectus.
This conclusion spawned headlines in a number of popular media outlets that challenged the validity of human evolution. (For example see here and here.) As is often the case, the headlines exaggerated and sensationalized the implications of these fossil finds.
The coexistence of H. habilis and H. erectus doesn’t directly challenge human evolution. It simply means that H. habilis didn’t evolve into H. erectus through a process known as anagenesis. (According to this idea, one species transforms into another with the original species disappearing.) Instead, H. habilis could have given rise to H. erectus through branching from the original population via a process called cladogenesis. Alternatively, H. habilis and H. erectus could have shared a common ancestor, though no evidence currently exists to substantiate this proposal.
While the coexistence of H. habilis and H. erectus doesn’t invalidate human evolution, this discovery highlights a couple reasons why it’s premature to claim that the hominid fossil record substantiates human evolution.
Human evolutionary models, even the ones that appear to be the best-established, are highly speculative and, at best, have tenuous support from the fossil record. Time and time again a single fossil find overturns a “well-established” idea in human evolution. It’s hard to know what other entrenched ideas will soon be abandoned as new hominid specimens are unearthed and studied. It’s hard to accept human evolution as a “fact” given the actual level of uncertainty about the relationships among the hominids in the fossil record and the constant flux within the discipline.
It is hard to know which hominid fossils are transitional intermediates and which ones are not. Prior to this most recent discovery, the hominids recovered in Dmanisi, Georgia, were considered important transitional intermediates between H. habilis and H. erectus that supported an anagenetic transformation. The coexistence of these two hominids means that the Dmanisi hominids can’t be transitional forms. This raises questions such as, “How many other transitional intermediates in the hominid fossil record have been misinterpreted?” and “Could it be that other key transitional fossils have been misclassified?”
For human evolution to be declared a fact, anthropologists must define the evolutionary route that transformed an ape-like creature into modern humans—replete with a progression of intermediate forms. The insight gained from this recent work highlights how far evolutionary biologists are from establishing this requisite understanding.
The H. erectus find holds surprises too. Next week I’ll describe what those surprises are and how they impact human evolutionary models.
For more information on the relationship between the hominid fossil record and human evolution, see Who Was Adam?
This statement I interperet to be the preconceived end result I talked about?
A ‘seeker’ is forever seeking the truth. The ancients decided the truth is whatever one wishes it to be,.
Now we need to figure who the "ancients" were and where they got their data? :o)
Ah ~ the voice of experience, weighs in. >:-}
If the truth is whatever one wishes it to be, why seek the truth when you can create it?
So, obviously you aren't seeking the truth, or you haven't made up your mind about creation and evolution. Just curious, which is it?
Seeking, is not my game. I commented on outlandish statements by “ truth seekers’
Having said that.....my mind remains open to all and any ideas. Crawling out of the muck or descending from the great Apes matters not.Whatever I think doesn’t change anything....what is , is, what is.
There are several kinds of facts. Scientific fact is its own kind of fact. There is a TOE, which is a fact whether the TOE per se is true. That’s another kind of fact, or two.
Evolution is a term that applies to several different things, at different levels. In that it is like many of our words.
First, evolution is a fact; by this I mean that change from generation can be observed and is not disputed. This says nothing about how or why that change occurs.
On another level, the theory of evolution seeks to explain all of the pertinent facts that are observed. At that level of abstraction, evolution is a theory, not a fact.
Here are a couple of definitions from my FR homepage which may help.
Theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses." Addendum: "Theories do not grow up to be laws. Theories explain laws." (Courtesy of VadeRetro.)Theory: A scientifically testable general principle or body of principles offered to explain observed phenomena. In scientific usage, a theory is distinct from a hypothesis (or conjecture) that is proposed to explain previously observed phenomena. For a hypothesis to rise to the level of theory, it must predict the existence of new phenomena that are subsequently observed. A theory can be overturned if new phenomena are observed that directly contradict the theory. [Source]
Observation: any information collected with the senses.
Data: Individual measurements; facts, figures, pieces of information, statistics, either historical or derived by calculation, experimentation, surveys, etc.; evidence from which conclusions can be inferred.
Fact: when an observation is confirmed repeatedly and by many independent and competent observers, it can become a fact.
Finally, in your discussion of Carl Sagan, you seem to be using "evolution" to include origins. It does not include origins. The theory of evolution will work just fine with natural origins, creation, space aliens, or panspermia as the source of the first life.
Evolution THEORY is a taxpayer funded BELIEF system (religion.)
Yes. They must have come from Hetero Erectus.
LMAO
Your question assumes something that is not a part of the theory of evolution, so let me take a moment to try to clear this up.
The theory of evolution does not postulate a lizard giving birth to a bird, or any other change of such magnitude. If this were the case, your question, where would an individual with such an extreme adaptation find a mate, would be a good one.
Rather, the theory of evolution suggests small changes, where one generation is almost the same as the previous, and there is no trouble interbreeding for any of the individuals in a population.
When two groups become separated those changes can move in different directions, and if the two populations are under pressure from environmental changes, they may drift apart rather quickly. In time, the two populations may no longer be inter-fertile, which is the definition of a species.
But, at no time would the theory of evolution suggest that changes from one generation to the next would be so extreme that an individual could not mate with other members of the population. Should such an extreme mutation occur, the theory of evolution would suggest that that individual would not survive to reproduce.
So now you're saying that you don't where we came from and you are not seeking to find out.
Hmm.
And that's better than someone seeking how again?
Your not clearly stated underlying guess that the author is a creationist may be right but the main point of the article is correct: the facts, all the facts collected so far do not support a theory of human evolution, which is what I hope one day will be the case!
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