Friday, April 19, 2013

Exploding Myths to do with Evolution (1)

Bashing assorted myths on evolution, especially the human version, is like playing 'whack-a-mole'. This is on account of the fact ignorant creationists have engineered whole-cloth lies and deceptions about it. In the process, they've roped in millions to believe their insane nonsense of 'Adam & Eve', a 6,000 yr.-old Earth etc. merits being taught alongside evolution. It doesn't: it merits being put into the nearest dumpster with their other swill.

So in this and the next part I want to highlight some of the most common myths perpetrated about Darwinian evolution. In many respects I already covered one several blogs ago, that was concerning the "missing link". So now we will look at some others.

1. If Evolution’s true then why don’t we see apes evolving into humans?

This myth errs in not recognizing that humans, apes and monkeys are all distant cousins, as opposed to species in the same SINGLE evolutionary path. Humans don’t come from apes but from a common ancestor that was neither ape nor human in the distant past. Also, it overlooks the algorithmic branching basis of evolution, see e.g.

Thus, multiple evolutionary offshoots (as shown above) confirm no (single) primate evolution is based on a single path. Thus in the past seven million years there have evolved multiple hominid species including Homo Habilis, Homo Erectus, and Homo Neanderthalis- all of which went extinct along the way- except modern humans or Homo sapiens. Meanwhile the idea of current apes evolving to humans totally turns this algorithmic-convergence on its head, and proposes a singly determined evolutionary path!

Less well known is the crucial role that dentition analysis and tool making play in sorting the fossils of prehistoric humans. For example, one of the first questions the investigator will ask is whether a given jaw and teeth found in it, can accommodate flesh eating. For some fortunate cases, this is also answered by the fossils found in the vicinity of the hominid ones. For example, in the case of one Au. garhi fossil (see image of this hominid) an antelope jawbone was found nearby and on it ancient cut marks disclosing its tongue had been sliced out using a stone tool. Radio-nuclide dating of both fossils traced them to the same time.

Obviously, genetic testing is the optimum or gold standard. In one of the most powerful ever demonstrations of the validity of human evolution, Yunis and Prakash, 1982, Science, Vol. 215, p. 1525, 'The Origin of Man: A Chromosomal Pictorial Legacy', showed that the human chromosome designated '2' was the result of the telomeric fusion of the two ape chromosomes, 2p and 2q. The effect also saw the reduction from 24 chromosome pairs in apes, to 23 pairs in humans. In other words, the duo of ape chromosomes (2p and 2q) can be considered prima facie evidence that humans and apes share a common descent.

2. No one’s ever actually seen evolution occur!

In fact, we do observe evolution happening especially with organisms (e.g. fruit flies, viruses, bacteria) that possess short reproductive cycles. The problem arises because creationists treat micro-evolution disparately from macro-evolution. Because they don't regard the former as part of a continuum leading to the latter, they consider "macro-evolution" the only genuine form. (By “micro-evolution” we mean minute evolutionary change, involving a small proportion of DNA. For example, the emergence of an orange-eyed fruit fly (drosophilia melanogaster) after 20 generations would demonstrate microevolution.)

Macro-evolution entails a proportionately large change in the DNA underlying it that probably reflects ongoing natural selection, over significant time. For example, the change from a cold-blooded dinosaur to a warm-blooded dinosaur that’s a precursor of modern birds would be a case of macroevolution.

The point missed by the Creationists (or perhaps they never processed it in the first place) is that it is hundreds (or thousands) of micro-evolution transitional components that engender macroevolution, whereas creationists think they are two totally distinct aspects that are unrelated. Once one accepts the two are integrated into one interwoven process then one can accept that we DO see evolution actually occurring as when fruit flies have altered their wing shape or eye color after 20 generations!

Once more, the key aspect that shows micro-evolution is real evolution is the fact that gene frequencies are observed to change (along with the fitness) as time goes on. Thus, it is not simply like "breeding cattle" or different species of dogs (for which many varieties may actually see the gene frequency alter in negative directions, with fitness reduced).

To fix ideas: gene frequencies help determine the success (and progress)  of natural selection. In natural selection there is a genetic "favoritism", as it were, for certain species' traits or characteristics to be passed on or selected out of a group of competing traits in the gene pool. In more technical terms, preferential alleles appear by virtue of their relative increase in gene frequency.

Two quantitative measures for success of natural selection are the fitness (w) and the selective value (s): These can be measured on either absolute or relative scales, but are related algebraically on the latter by:

w = 1 – s, or s = 1 – w

As an illustration, consider a cockroach species (Blattella germanica) with allele D, where D denotes resistance to the pesticide dieldrin, and d denotes non-resistance. In the population after some defined time, let three genotypes be exhibited in the population: DD, Dd and dd.  Now, on average over time let each dd and Dd individual produce one offspring, and each DD produce two. These average numbers can be used to indicate the genotype’s absolute fitness and to project the changes in gene frequency over succeeding generations. The relative fitness (w) is meanwhile given by:   w = 1 for DD

w = 0.5 for Dd

w = 0.5 for dd

The selection values, or relative measures of the reduction of fitness for each genotype, are given respectively by:

s = 1 – 1 = 0 for DD

s = 1 – 0.5 = 0.5 for Dd

s = 1 – 0.5 = 0.5 for dd

As we expect, the dieldrin-resistant genotype displays zero reduction in fitness, and hence maximum survival rate. By contrast the d allele can be regarded as ‘deleterious’. Indeed, it can be shown that over successive generations of roaches, the gene frequency (of d) will decrease by:

D q= -spq2/(1 - sq2)

Here p is the frequency of the favored allele, and q the frequency of the disadvantaged (‘deleterious’) allele. Let’s say at a particular time a gene frequency ‘snapshot’ of the cockroach population under study yields: p(D) = 0.60, q(d) = 0.40, i.e. the favored allele D is reproducing at the ratio 3:2 relative to the disadvantaged one, d. Then one can work out how the alleles' frequencies vary over multiple generations. Of course, since the fundies - most of them- can't do simple algebra, this will be beyond them they will never accept it!

3) Evolutionists claim the process occurs by random chance.

Not so. Natural selection is not “random” nor does it operate by “chance”. What happens is that once a particular mutation is stabilized, then natural selection preserves the gains and eradicates the mistakes (to enhance better adaptation). Meanwhile, "chance" would be like me sitting a monkey down in front of a type writer or computer keyboard and hoping there is some "chance" it will type out at least one page of coherent script. But since a monkey will likely not recognize any key - or even if it does, then make a connection to words, or how to compose them into articulated thoughts - this isn't likely. It all rests on CHANCE!

Meanwhile, natural selection rests on preferred steps each of which consolidate former steps while advancing the adaptation. Thus, the eye evolved from a single light sensitive spot in a cell to the complex organ we behold today not by chance but rather by thousands of intermediate steps – each preserved because they assured better adaptation if incorporated, and hence a better eye. Many of these steps can still be observed today in simpler organisms.

Richard Dawkins perhaps put it best:

"What natural selection does is to consolidate particular random mutations into a more stable, adaptive adjustment – governed by deterministic factors and inputs. Thus, that while the selected trait often appears at random, its preservation in the gene structure cannot be relegated to randomness”

Again, his distinction between deterministic and random factors and inputs is perhaps too subtle for creationists and their ilk to comprehend. After all, most have never taken even a high school biology course, far less a college level one.

4) The Second Law of Thermodynamics disproves Evolution

This myth commits at least two fundamental errors:a) The error which assumes that evolution means more primitive organisms develop into more complex or organized ones, and, b) The error that the second law (because it refers to increasing disorder or "entropy") applies to all living things- hence it is impossible they can "evolve" to more orderly, organized forms.

Consider (a) first: At no point and no place do evolutionists claim that more organized forms are the inevitable manifestation of natural selection and adaptation, and represent evolutionary success.What evolution states,which any high school biology student learns, is that the species which survive best are the most well adapted to their environment.

Thus, the humble cockroach beats just about all other species on Earth for evolutionary success given it's been around for 150 million years. Humans, though much more complex and organized than cockroaches, have only been around in their modern form for barely 1.5 million years, if that. Humans, up to now, have enjoyed  barely 1/100 th the evolutionary success of the cockroach, measured in time!

Now, as to (b), this is a common error of those who've never taken advanced physics, but just read Googled excerpts. It's basically a direct result of misinterpretation of the 2nd law, something I often see from those who've never taken a serious physics course. Strictly speaking,  the law states:

Entropy (the state of disorder) will tend to increase over time in any closed system

This is generall expressed in statistical mechanics terms as:

s = log g

Where 'g' denotes the number of accessible states. In other words, in a closed system we will expect the probability of increasing entropy and that means increasing accessible states.  This was discussed at length when we looked at assorted spin systems (see the series on 'Order and disorder' earlier this month) and noted that higher entropy - as in a state with low excess spin- corresponds to the most probable state. Say a  closed magnetic spin system S(2), has 10 spin ups while S(1) has five, then S(2) has a much higher degree of order (less entropy) than the system S(1). 

The part about closed systems is very crucial since it is exactly the part that the creationist-ID crowd omits, which renders their complaints using the 2nd law non-starters. The reason is that neither the Earth nor its biological systems are "closed" systems, hence do not exhibit constantly increasing disorder. The Earth, for example, receives a constant input of radiant energy from the Sun - quantified as some 1360 joules per square meter per second. Plants on the Earth are likewise OPEN to solar energy, and receive it and then use it in the process of photo-synthesis.

Since Earth is an open-dissipative system then at any given time for any subsystem, entropy may decrease and order increase, thus life may evolve without violating any natural laws.

Bottom line: so long as the Sun is radiating its energy, life can continue thriving and evolving. (Thus, more highly organized organisms such as humans have had the capacity to emerge, by dint of this input energy which they've been able to consume and retain - if only briefly).

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