farmerman wrote:RLQuote:Q -- How do you know that X evolved from Y ?
A -- Because they are different species.
Q -- Why are they not considered the same species?
A -- Because we know that X evolved from Y.
Actually the argument goes more like this
A Did X and Y share common ancestors?
B. Lets look at the genetic makeup of the li
ving species, evidence of the fossil record,evidence of time and biogeographic distributions of X and Y. Also, let us compare the data that continental drift or other tectonics provides to understand the issues of the fossil record.
C. We conclude that X and Y share evolutionary predecessors and are strongly linked by evidence.
Inferences like this are simply that. Inferences.
Correllation is not necessarily indicative of causation. For instance, we may note that nearly all billionaires are above 30 years of age. Does that mean that achieving the 30th year is in some way causative to earning a billion dollars?
C'mon.
Quote:genetic makeup of the living species
Why would it be surprising that two critters that live in the same or similar environments should be found to have many of the same genetic patterns to produce similar features (but necessarily identical) that will enable them to survive in the same environment and feast on the same diet, and overcome the same challenges of weather, predators, topography , etc ?
It doesn't mean that one 'evolved' from the other.
Or in some cases, as we have discussed, what are regarded are 'separate species' may actually be of the same stock, but artificially and arbitrarily labeled as separate for the convenience of taxonomists.
Quote:evidence of time and biogeographic distributions
Similarly, the fact that one species is found to be more numerous than another at various times or in various locales doesn't mean that one 'evolved' from the other. What would be surprising would be if we determined that two critters happened to have ALWAYS had the same numbers of population at all times and in all places.
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If evolution is occurring now, it should be evident in literally millions of living examples of critters in transition, with new organs, biological systems etc sprouting up everywhere.
But we don't see this at all. The few weak examples that are usually pushed forward of modern day evolution are fish that produce fish and bacteria that produce bacteria.
Quote:And if enough generqtions go by and if a population is isolated from its kin, then is a new species born
Sexual isolation of a population is known to produce largely negative (or at best, neutral) results among humans, not newly evolved 'species'. The negatives are often evident within just a few generations. But this is the process by which great leaps forward in evolution are purported to have occurred.