I Hear many talking about all the transitional evidence. Should be easy. I am also interested in how scientists decide what is descendant from what.
With fossils, it's usually impossible to identify direct ancestor-descendant relationships. There are exceptions: in cases where a clear morphological succession is preserved in a clear continuous stratigraphic succession (as in: in successive layers at the same location), you can fairly securely infer direct descent. (Prothero's book about transitional fossils discusses examples, mainly from microorganisms,
see here.)
Usually, the fossil record is not so kind to you, because at any one location there are likely to be gaps in time, gaps in the creatures that were "lucky" enough to be preserved, and so on. Therefore, the best you can normally do is perform phylogenetic analyses and determine the order in which different groups branched off the family tree. In actual family tree terms, you can't tell mothers from aunts, but you can often tell one generation from another.
In the case of whales, there have been a couple that were said to be ancestral but now are not. One was based on teeth?
Can you be more specific? Whales are not my thing, but maybe I can find more info for you...
If I was an evolutionist, I would be skeptical of that anyway. Where is the real science behind common ancestry? Is there anything outside the educated guessing that is routine?
Yes. The evidence from phylogenetics is statistically incredibly strong. See
here for details, but if you have no inclination to click links, here is my version:
(1) Common descent predicts a tree of life. Prokaryotes are rather liberal with their gene swapping, so they are rather more complicated. However, on a broad enough scale, the evolution of animals and plants MUST be tree-like based on all we know about what they can and can't do. For example, animals and plants are often observed to hybridise with closely related species, but
only with close relatives. Two ragworts may give rise to
fertile hybrids, but a ragwort and a rose wouldn't. Therefore, if all [insert group] came from a common ancestor,
they must have done so by the repeated branching of lineages. A tree.
(2) There is a mind-boggling number of possible trees. There's a calculator at
TalkOrigins to give you exact numbers, but the important fact is that they are absolutely huge. Take just
ten species, and there are
millions of possible ways in which they could be arranged on a tree. If the species were not related by descent,
all of these would fit their traits equally well.
(3) Yet trees derived from independent data sources agree. Whether your calculations are based on morphology, DNA or protein sequence, or in some cases, even the possession of certain genes, they give similar trees. They don't agree
exactly - no two measurements in the real world ever do. No model of evolution is perfect, some evolutionary scenarios make it hard or impossible to infer the exact relationships of lineages, and many tree search algorithms are not guaranteed to find the best tree even if everything else is dandy*. But they all point to a very small subset of the many possible trees. Essentially, they are the same within measurement error.
The fossil record is an amazing insight into the history of life, but even without it, the evidence for common descent would be overwhelming.
*Incidentally, this is precisely because there are so many different trees to explore. Even with a non-exhaustive search, a large phylogenetic analysis can take days on a powerful computer. Instead of evaluating all the possible trees, the algorithms generally take a starting tree - which could be random, given by the user or derived from a simpler, quicker method -, make random adjustments to it, and accept or reject the result after comparing it to the previous tree. (Rinse and repeat a few million times) Which, fittingly, is a very
evolutionary approach.
YOu talk about speciation like it is something quantitive. Like they come with a plack. Speciation only what evolution scientists agree it is. They don't even know yet how to define a speicies. It is very controversial.
You mistake controversy over the best definition of species for an inability to make the concept useful.
True, the most appropriate species definition differs from situation to situation. For bacteria, the biological species is meaningless. Likewise for fossils. If you are an ecologist, maybe you couldn't care less about the tangled evolutionary history of a species complex and want to focus on the niche they fill instead.
Speciation, however, involves genuine, quantifiable phenomena. Speciation is specifically used to refer to the formation of new
biological species. The study of speciation is the study of
reproductive isolation: what are its genetic mechanisms, how factors such as standing genetic variation, ecology or geographic barriers affect it, how genes can and cannot flow through hybrid zones, etc.
Incidentally, the concept of speciation is pretty useless for fossils for this reason.
I would like to ask you what happens after speciation?
Divergence.
At what point does a species of fish turn into a species of reptile?
Depends on your definition of fish and reptile.
ETA: This is why I don't like defining macroevolution by speciation:
speciation and major change are not strongly coupled. There are cryptic species that can only be told apart by DNA barcoding, and conversely, many biological species exhibit a lot of morphological variation. (You could even argue that humans are one such species!)
Where is the evidence speciation leads to body plan changes and not just enumerable species of fish, birds, horses, whales, monkeys, humans?
What do you think fishapods and theropod dinosaurs are?
How long were they wrong about Neanderthals? They were brutes, stupid, and slow, much like those who believe ID theory. Now we know they decorated, built structures, buried their dead, and interbred with other humans.
That's just standard human arrogance for you.
Isn't it interesting and convenient, how evolutionists can't really show how major change happens. Its always mysterious and out of site blanketed in millions of years. When it is challenged the only response is, "you don't know how evolution works". Seems no body does, it is just taken on faith it does.
Hogwash. Let me pull out a little selection for you - partly about actually observing major change, partly about understanding the mechanisms.
How developmental constraint may influence wing pattern evolution in butterflies.
A viable natural hopeful monster.
The role of a Hox gene in the origin of placental mammals.
Observed switch to a simple form of multicellularity.
The genetic basis of pelvic reduction in sticklebacks.
The genetic basis of appendage diversity in crustaceans.
So yeah, you might want to bother learning what we actually understand about major change before you start making claims like that...
Anybody see the hypocrisy here? ID is expected to prove who and what the designer is, or its not a theory.
In all honesty, ID should first propose some objective criteria to detect
design. I couldn't care less who you think the designer is - until you can show that we should be looking for one in the first place, it's a moot point.
While common descent gets a pass because it cannot be shown how it happens. It cannot be determined where or when it happens,
All over the planet, duh.
or even how long it takes to happen.
Well, the fossil record is rather good for
that purpose.
Incidentally, have a how-fast-it-happens study about
body size evolution in mammals.
Evans et al. 2012 said:
Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. [...] Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases.
