Uncommon or Common Descent?


(Ashwin S) #90

Ok fair enough.
I recently read a peer reviewed paper where a bunch of scientists were pushing for panspermia… Basically theorising that DNA from space seeded the biosphere with all the innovation required (for example the Cambrian explosion, octopuses and what not).
Their basic contention is that all these organisms appeared suddenly and enough time was not there for them to evolve.
So you have some company there with respect to skepticim of evolution… Though their solution is kinda crazy.
I really don’t see why some versions of special creation cannot be published if stuff like panspermia can be.


(S. Joshua Swamidass) #91

Common descent is the hypothesis that a set of distinct species today share ancestors in the distant past. That is it.

From there, it different more specified hypothesis can be offered. For example, we can test if “chimpanzees and humans” share common ancestors; this is the “common descent of man”. We can also assert or wonder if “all life on earth today” shares common ancestors; this is “universal common descent.”

We, here at Peaceful Science, focus in on the common descent of man. No one cares whether bacteria share a common ancestor. A lot of people care whether humans and chimps share a common ancestors. Here, also, the evidence is much much stronger.

Does that help?


(T J Runyon) #92

Yeah but that paper has taken a beating and actually has been laughed at. Philosopher of biology Peter Godfrey Smith discusses it here: http://metazoan.net/63-octopuses-not-from-space/


(S. Joshua Swamidass) #93

We covered that here too: Octopus not an Alien.


(T J Runyon) #94

Oh yeah! Forgot about that thread


(Ashwin S) #95

What’s the big fuss about it then? I am sure even some YEC guys would affirm that a set of distinct species share ancestors in the past… (of course they wouldn’t agree for UCD, and stop at the point where they define kinds).
And the other contention is regarding how novelty arises. Suppose God used viruses to change how genes are regulated and created new species in some cases. Why should it be called common descent? After all the focus should be on the vehicle of change. Why not viral descent? Or natural genetic engineering? Or unnatural genetic engineering if you happen to be a creationist… the point is, there are mechanisms in which descent becomes trivial to the evolutionary event.
In such cases, would you agree to call it something else?

I am sure some people care.I certainly do.I find theories on bacterial evolution fascinating. I am sure there is a lot we can learn about how unicellular organisms evolve that can inform us about human evolution. The big picture is always important.

I am trying to go through this stuff. What bugs me about the human evolution story is the difference between when civilisation arose and human beings emerged. I find it very difficult to assume that “modern humans” were around for hundreds of thousands of years while civilisation started out only about 20000 years ago.

Yes it does help…


(Ashwin S) #96

My point is that it was published. So why not the same treatment for special creation or ID. Publish and then discuss/trash etc.
Afterall the arguments are similar. The only difference seems to be philosophical implications connected to the conclusions.


(S. Joshua Swamidass) #97

The big fuss has always been about the common descent of man.

That is all independent of common descent.

Sure, but there isn’t durable conflict here. We can certainly talk about bacterial evolution, and we do.

Have you seen the Genealogical Adam yet? This solves the problem.


(Ashwin S) #98

If common descent becomes compatible with any mechanism … wouldn’t that make the idea itself useless in terms of explaining anything?

I have gone through Genealogical Adam. It doesn’t solve the problem. Unless you are claiming Adam was superior in intelligence or had some other special quality that kickstarted civilisation.In which case, you are arguing against the common descent of modern humans.(atleast with respect to he qualities that make us different from animals).


(T J Runyon) #99

A lot of that has to due with environmental factors. Ice ages etc. if you are interested in discussing this more I can split it into a new topic


(S. Joshua Swamidass) #100

You mean something like the tree of knowledge? Oh wait, he had that…


(Ashwin S) #101

Just point me to link. I will read up… and ask if I have any doubts.


(George) #102

@Ashwin_s

Forget the words “common” and “ancestry”. The concept, symbolized by any word or phrase you might choise, is that over time, all populations experience genetic changes and other changes that drive the reproductive success of future generations made possible by the current environmental factors affecting each sub-population.

This is theoretically applicable the moment genetic life is established - meaning:

  1. If you believe there was an ark full of animals, these evolutionary changes begin once again, as soon as they were released from the ark and began exploiting other niches of the environment.

  2. Even if you believe God created multiple templates (of “kinds” or species)… genetic diversification begins immediately with the very next generation. There are no known factors that limit how much a genome can change each generation … Except how much we think God wants to promote change in any given population.

  3. But factors that DO affect the degree of influence any one mutation can have has nothing to do with darwinism… but more to do with mathematics:

a) size of the population in which a given mutation occurs;
b) sampling probability of a sub-population moving into a more isolated reproductive pocket;
c) and the sensitivity to change is the configuration of alleles involved in successful fertilization of the next viable generation.

As you can see, these forces are not mysterious … nor do they require any particular form of mysticism for them to apply to each and every life form that replicates by means of DNA or RNA.


(Ashwin S) #103

Ok, can this be tested… is there evidence of some kind of biological evidence for increased cognition, linguistic ability etc say twenty thousand years ago?


(George) #104

@Ashwin_s,

20,000 is too recent …

But there is an identifiable curve in throat anatomy and brain size and anatomy in the hominid branch of the PRIMATE family compared to all the other branches (chimp, gorilla, orang, etc).

And usually all that has to be done to favor the evolutionary interpretation is either:

  1. collect a preponderance of evidence that the earth is not less than 10,000 years in age;

  2. and/or that there was no period of visualization where human remains were preserved on comparable geological horizons until approximately 100,000 years ago.


(Ashwin S) #105

I think the Key question is the degree of change and when and how it happens. We have empirical evidence that species generally don’t change beyond a limit. For example the duck bill Platypus has remained the way it is for millions of years. There are built in mechanisms in a genome that make it stable at a species level.

I understand changes being fixed in a population. However I would categorise any change which needs God’s direct involvement as ID or special creation. Evolution needs to be stochastic.


(Ashwin S) #106

@swamidass proposal would require a sudden change in these capabilities.
20000 years was just a ball park figure.
If it was gradual change as you indicated, then @swamidass proposal would be against the empirical evidence.
He has claimed that it is matching with the current understanding. Hence my question to him. Let him answer as per his convenience.


(George) #107

@Ashwin_s

I believe we find that where there is little phenotype change it is because there is little change in the environment. Crocodiles as a population appear to have changed little because the nature of the environment typical to the interface of waterfront and land is relatively stable. And where it is not stable…the population contracts or expands in geographic range.

There are indications that the platypus was ORIGINALLY a land-based creature that survived by adapting to water.

So … maybe you should develop better empirical evidence to prove your point.


(Ashwin S) #108

George,
These are just so stories that work either way. It amounts to
1). Organisms evolve to become better suited to their environment.
2) Organisms don’t evolve over a long period because they are well suited to their environment.

If I wanted to hear fairy tales, I would read that genre of literature. I don’t need that from so called scientific claims.


(George) #109

@Ashwin_s,

And yet you are perfectly content to inflict fairy tales on everyone when you suggest that chromosomes somehow KNOW not to change beyond some invisible limits.

… or that the distinctly peculiar monopoly of marsupial mammals in Australia can be explained by ANYTHING involving a global flood, rather than than Old Earth scenarios plus common descent.