Login

Join for Free!
117036 members


Experimental evidence for evolution

Discussion of everything related to the Theory of Evolution.

Moderator: BioTeam

Experimental evidence for evolution

Postby curiousgeorge » Wed May 19, 2010 3:37 pm

I have been reading about evolution recently in an attempt to understand it.

My question is whether there have been any experiments conducted that provide empirical support for macroevolution. Has there been any experiments that show an organism changing to something different?

I read about the fossil record and the theory in general but my question is about experiments.

appreciated.
curiousgeorge
Garter
Garter
 
Posts: 4
Joined: Wed May 19, 2010 3:22 pm

Postby JackBean » Wed May 19, 2010 4:14 pm

I don't know experiments, but there are some observations of evolution in nature (e.g. seeds of plants in wild and city; some birds etc.)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
User avatar
JackBean
Inland Taipan
Inland Taipan
 
Posts: 5667
Joined: Mon Sep 14, 2009 7:12 pm

Re: Experimental evidence for evolution

Postby curiousgeorge » Wed May 19, 2010 4:26 pm

Thanks for the reply jack.

Are these observations considered to provide empirical validation for macroevolution?

What birds + plants are you referring to?
curiousgeorge
Garter
Garter
 
Posts: 4
Joined: Wed May 19, 2010 3:22 pm


Re: Experimental evidence for evolution

Postby skeptic » Thu May 20, 2010 7:47 am

There have been thousands of experiments carried out to explore the process of biological evolution. Since it takes numerous generations to create a new species, or anything close, most of these experiments have been done on micro-organisms or such things as fruit flies. These are rapidly reproducing organisms that go through many generations in a short time.

For example, culturing bacteria on nutrient agar, and slowly removing an essential nutrient to see if evolution will equip the bacteria to be able to develop new enzyme systems to manufacture that nutrient. It does, if the change is across enough generations.

Numerous similar experiments have shown the way bacteria adapt to the presense of antibiotics, and develop ways to neutralise them.

Experiments on large animals and plants are less common, and focus on smaller levels of change. For example : published in the New Scientist magazine (15 May 2010 issue, page 12) is an experiment in the Caribbean on lizard evolutionary change. Whole islands were isolated by surrounding them with nets, to manipulate the level of predation and competition to see what influence was most important in driving evolutionary change.

Cichlid fishes (from lakes in Africa) have been observed and manipulated to observe the process of evolution. At least one new species has been followed over a 100 year period, and recoerded as developing into a new species.
skeptic
Coral
Coral
 
Posts: 119
Joined: Tue Apr 14, 2009 2:44 am
Location: New Zealand

Re: Experimental evidence for evolution

Postby curiousgeorge » Thu May 20, 2010 4:24 pm

Thanks skeptic.

I've read about the bacteria and the fruit flies in several articles, but as you said those are examples of minor changes (micro-evolution)

I am particularly interested in the cichlid fish example though. How did it change to signify that what we observed was macro-evolution? Do you have any additional information?
curiousgeorge
Garter
Garter
 
Posts: 4
Joined: Wed May 19, 2010 3:22 pm

Re: Experimental evidence for evolution

Postby skeptic » Thu May 20, 2010 7:56 pm

CG

The cichlid example was written up a few years ago in Scientific American. Cichlids in the fresh water lakes of Africa are amazingly diverse. Genetic or geographic isolation appears to be the key, leading to rapid speciation. These fishes have been observed and described by naturalists for at least 100 years, and at least one population has been observed over that time to become isolated and then change sufficiently so that it will no longer breed with its original stock.
skeptic
Coral
Coral
 
Posts: 119
Joined: Tue Apr 14, 2009 2:44 am
Location: New Zealand

Postby Darby » Fri May 21, 2010 9:32 pm

If you found, in Nature, chihuahuas and mastiffs and poodles and spaniels, would you classify them as different species? It is artificial selection, which drives specific traits to extremes quickly, but it is kind of "proof of concept" results.
Darby
Viper
Viper
 
Posts: 1262
Joined: Thu Mar 02, 2006 5:29 pm
Location: New York, USA

Re: Experimental evidence for evolution

Postby curiousgeorge » Mon May 31, 2010 4:28 pm

Darby,

Dog breeding is not really something I would consider evidence for macroevolution.

My question pertains mostly to any evidence showing something changing to something novel or something drastically different if you like.

Is there any study/evidence for this?
curiousgeorge
Garter
Garter
 
Posts: 4
Joined: Wed May 19, 2010 3:22 pm

Postby SelfishGene » Mon May 31, 2010 7:22 pm

Observed instances of speciation:
http://www.talkorigins.org/faqs/faq-speciation.html

This experiment may also interest you, however it is not speciation:
http://en.wikipedia.org/wiki/E._coli_lo ... experiment
SelfishGene
Garter
Garter
 
Posts: 17
Joined: Tue Mar 16, 2010 6:27 am

Re: Experimental evidence for evolution

Postby skeptic » Mon May 31, 2010 8:01 pm

Here is a reference to chichlid evolution, that has been observed to happen over 100 generations.

2010 http://www.newscientist.com/article/dn1 ... speed.html
skeptic
Coral
Coral
 
Posts: 119
Joined: Tue Apr 14, 2009 2:44 am
Location: New Zealand

Re: Experimental evidence for evolution

Postby jevg » Thu Jun 17, 2010 11:32 pm

The Long Term Evolution Experiment (LTEE) has been going on since 1988.

http://www.pnas.org/content/105/23/7899.full.pdf+html


By way of some background, Evolutionists debate a lot about how evolution works. Stephen Jay Gould suggested that sometimes mutations happen that have no immediate benefit; but those mutations remain in the gene pool because they are not harmful. Those mutations are just floating in the gene pool waiting to be used. Then a subsequent mutation that depends upon those previous mutations can occur that causes some benefit to the organism. In other words, a new mutation might depend upon other mutations that happened in the past. Scientists call this, “historical contingency.” “Historical contingency” simply means, “it depends upon something that happened in the past.”

Gould’s opponents say that the environment drives evolution to a particular solution, so it doesn’t depend on past accidents. Furthermore, a mutation that has no immediate benefit will likely disappear from the gene pool before it is eventually needed

The Experiment

They started out with 12 individual, identical E. coli bacteria and put each one in its own little Petri dish; and they grew into 12 colonies.
E. coli bacteria reproduce asexually. In simple terms, the bacteria grow bigger and bigger until they get large enough to split in half, so the parent cell turns into two identical child cells.. Although the division process nearly always produces two identical children, sometimes the process partially fails, producing mutant offspring.
It takes nearly 2 hours for E. coli bacteria to reproduce, so there are about 6.5 generations born every day. This is convenient for scientists because it allows them to study lots of generations in a reasonable amount of time.
So, if you start out with 1 bacterium, you will have 2 in about 2 hours, then 4 two hours later, then 8 two hours after that, then 16, then 32, then 64, and finally 128 in just over a day. It is very convenient that the colony grows by a factor of roughly 100 every day.

They fed them glucose and citrate, and gave them 12.2 times more citrate than glucose. This was critical because E. coli can’t digest citrate.. E. coli would die on a steady diet of citrate.

The goal of the experiment was to try to force the E. coli to evolve in such a way that they could digest citrate, like some other bacteria can.

They did this by giving the bacteria just enough glucose to keep them alive, and an abundance of citrate. The expectation was that if the E. coli did evolve into a form that could digest citrate, that new variety would flourish in the citrate-rich environment and drive the old variation to extinction.

One important caveat is this.
If you read the fine print, you will discover that E. coli can ALMOST digest citrate.

Result

It took more than 30,000 generations to fully evolve a capability that was already almost there, and it only happened in 1 out of 12 populations.

Thirty-thousand generations isn’t a long time for a bacterium, but 30,000 generations for people is about 600,000 years.

They really had to try hard using all the evolutionary pressure they could muster, to produce this minimal change.

However there was one unexpected result from this experiment.

QUOTE from the paper

The origin of the Cit+ function also had profound consequences for the ecology and subsequent evolution of that population. This new capacity was refined over the next 2,000 generations, leading to a massive population expansion as the Cit+ cells evolved to exploit more efficiently the abundant citrate in their environment. Although the Cit+ cells continued to use glucose, they did not drive the Cit– subpopulation extinct because the Cit– cells were superior competitors for glucose. Thus, the overall diversity increased as one population gave rise evolutionarily to an ecological community with two members, one a resource specialist and the other a generalist.


One of the fundamental ideas behind the theory of Darwinian evolution is extinction. Natural selection allows the group that is more fit for survival to drive the less fit ancestors to extinction.
In this experiment, the new variety did not drive the old variety to extinction.

Presumably that is because there was enough food for both varieties. Hasn’t there always been enough food for just one transitional form to survive, at least long enough to leave some fossils?
The primary thing we learn from this experiment is how difficult it is to cause even the smallest amount of evolution.

The LTEE showed that after 20 years of extreme, relentless pressure, it is possible for a minimal improvement in digestion to occur (after just 30,000 generations ).

How many generations it would take to develop a whole digestive tract from teeth to anus.?

The experiment is still continuing having reached about 50,000 generations with no additional results.
jevg
Death Adder
Death Adder
 
Posts: 50
Joined: Thu Jun 17, 2010 4:51 pm
Location: South Wales United Kingdom

Postby jevg » Mon Jun 21, 2010 4:13 pm

The Long Term Evolution Experiment (LTEE) has been going on since 1988.
Some more detail of terms of the experiment.

When I stated in my last post that E. coli can ALMOST digest citrate” this was deserving of a little more explaination.
E . coli already has a number of enzymes that normally use citrate and can digest it . However, it lacks an enzyme called a citrate permease which can transport citrate from outside the cell through the cell’s membrane into its interior. All that was needed therefore to use citrate, was to find a way to get it into the cell. The rest of the machinery for its metabolism was already there.
Lenski put it this way “The only known barrier to aerobic growth on citrate is its inability to transport citrate under oxic conditions.

The team have not been able to track down the mutation(s), however the point that the paper emphasizes is the historical contingency of the new capability. The evidence shows that in only one of the 12 population lines, and after some 20,000 generations a “potential” ( potentiating mutation) occurred that allowed at least a second mutation after 30,000 generations to give rise to the new citric capability.

So Richard Lenski is affirming that the evolution of some pretty simple cellular features likely requires multiple mutations.

If the development of many of the features of the cell required multiple mutations during the course of evolution, as this continuing experiment suggests, then this is another reason why Darwinian theory does not provide the answers to cell development.
jevg
Death Adder
Death Adder
 
Posts: 50
Joined: Thu Jun 17, 2010 4:51 pm
Location: South Wales United Kingdom

Next

Return to Evolution

Who is online

Users browsing this forum: No registered users and 0 guests

cron