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Consider the admission, within the past six months, by the Harvard psychology professor and evolution advocate, Steve Pinker. On the web site edge.org, Pinker revealed that he only recently came to accept that human evolution did not stop thousands of years ago. It is welcome news that Pinker has reached this understanding, but it is a bit surprising that he would have entertained his prior view at all. Highly persuasive evidence, which did not in fact exist, should have been necessary to conclude that human evolution had reached a standstill.
If organisms of any species harbor phenotypic variations that are capable of being inherited, and these phenotypic variations influence the numbers of descendants an organism is likely to leave, then the distribution of phenotypes (and genotypes) in the population will very likely change over time. In other words, the population will evolve. Thus, heritable variation that influences reproductive success is necessary and sufficient for evolution to occur unless the selective "forces" acting on the population happen to be perfectly balanced, which is highly unlikely. So the continuation of human evolution should be anyone's default assumption given that, as Pinker might have known, humans exhibit substantial genetic variation that could plausibly influence reproductive success.
In fact, there are numerous experimental reports on the allelic diversity at individual human genetic loci, as well as studies offering evidence of selection for or against alleles at particular loci, such as the lactase and Duffy blood group loci. Furthermore, recent studies designed to exploit the vast number of genetic markers now defined for the human genome, along with relatively new and sophisticated methods to detect selection, have provided evidence of selection at numerous human loci, and have, in one case, suggested that the pace of human evolution has accelerated in the past 40,000 years, in parallel with greater population size.
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Darwin, who I think can reasonably be regarded as the greatest applied logician since Euclid, introduced into biology the notion of categories for which membership was not all-or-none. Categories with absolute criteria for inclusion had been the norm in mathematics and logic for two millennia, but with Darwin's emphasis on evolving lineages, the intellectual community was given a powerful new tool. Thus, two humans (or members of any other species) do not have to share an identical list of attributes to qualify for membership in the species. Only some attributes (and a variable subset at that) must be shared.
Astonishingly, even today, many who regard themselves as Darwinians (or
neo-Darwinians) continue to construct and use biological categories that have more in common with those of ancient Greek thought than of Darwin's. For example, in my own field of immunology, it is common to distinguish between putatively innate and putatively adaptive immune mechanisms as if there were an absolutely obvious boundary between the two. Yet the actual mechanisms show little respect for this distinction, as when antibodies (adaptive) mediate immunity by interacting with phagocytes (innate). One of the most dramatic examples of the limitations of rigid categories in biology is the very notion of "species," for which there is still neither a consensus definition nor one that applies equally well to all types of organisms. Perhaps that is why the eminent population geneticist and evolutionary biologist, Richard Lewontin, once remarked that "Biology remains in many ways obdurately Platonic."
Neil Greenspan
mail@the-scientist.com
Neil Greenspan is a professor of pathology at the Case Western Reserve University School of Medicine. His research, clinical, and teaching interests relate to immunology and allied fields and are informed by his study of evolution. Greenspan and about fifteen Case faculty colleagues have organized a Celebration of Darwin and Evolution spanning the 2008-2009 academic year. Details can be found at: www.case.edu/darwin/.
[Comment posted 2008-05-18 11:34:13]
Dear Ruth Lamarck;
Surgery has nothing to do with heridity.
[Comment posted 2008-05-18 11:29:35]
[Comment posted 2008-05-15 14:02:41]
[Comment posted 2008-05-14 22:10:53]
All I said is that in order to develop individual traits which an organism does not have when it starts life as an individual organism, the organism has to develop, and this development invariably occurs under inseparable effects of both genes & environment, (plus the inseparable effects of that which already exists at each point along this developmental process).
So when you deal with development, you can never ignore the environment. The two are inextricably related, but, by no means are they identical. Development is a process. The environment invariably plays a role in this process, and the role it plays is inseparable from the role played by genes, and the role played by everything that the organism already has.
[Comment posted 2008-05-14 15:58:50]
OK, I see what you are talking about now. Of course an organism would normally have to develop to express a phenotype (although not necessarily in the case of some lethal alleles, but I'm not going to get picky). So the albinism trait isn't going to be expressed unless the organism develops, so perhaps by environment you are talking about development, is that correct? I do agree that the environment can play an important role in many phenotypes, and certainly development would play an important role in the expression of any phenotype associated with an organism after it is born! :) Thank you for expanding on your thoughts, I understand better now. Smile and enjoy conversing!!
[Comment posted 2008-05-14 15:20:22]
The simple fact is that you are wrong; you cannot have sickle cell disease without the two copies of the gene - one from each parent.
Genetics proves you wrong; my beautiful hazel/green eyes prove you wrong; my purebred dogs proves you wrong. Luckily for us, the neolithic people who pioneered agriculture figured out something that you still haven't grasped. You are just wrong.
You persist in your trivialities and fail to put forth a convincing argument, or (even better) research to support your fantastical thesis that there is no such thing as inherited traits.
It's clear you know nothing about biology, you likely read something about epigenetics but never understood it.
[Comment posted 2008-05-14 13:28:37]
The finding that specific genes are essential for the development of a specific trait, (including a specific disease), in a specific organism, does not mean that the presence of those genes is also sufficient for the development of that specific trait.
All individual traits develop in the individual organism under inseparable (!) effects of both (!) genes & environment, (plus the inseparable effects of that which already exists at each developmental stage). In other words, the presence of the essential genes is never also sufficient.
Except that such a brief statement would have been very difficult to understand without the far more detailed explanation I provided.
The point is that during individual development "essential" genes are never also "sufficient" for the development of a specific trait. For such a trait to develop you need the the "essential" genes PLUS the "essential" environment, (whose effects are inseparable from the effects of the genes, because the SAME genes can function differently in DIFFERENT environments, and the same environment can DIFFERENTLY affect the functioning of DIFFERENT genes).
[Comment posted 2008-05-14 02:55:49]
Medical experts often refer to specific diseases as "hereditary", or genetic diseases, when they know which genes are essential for the disease to develop. But it is misleading to assume that the terms mean that the disease develops without any effects of the environment. This is what I mean!
A fertilized human egg never has cystic fibrosis, (nor any other disease that can develop in humans only at a later stage). To develop such a disease, the fertilized egg must, (among others), develop all the organs that show the symptoms of the disease, and all these organs can never develop without an effect of proper environmental conditions, which may differ from one stage to another.(A human embryo does not need to breath, be fed, or cleaned. But a new-born child certainly needs all that. And so on.) So you can never exclude the effects of the environment, and assume that a "hereditary" disease can develop without any environmental effects.
Apart from all that, who knows? Maybe medical experts will one day discover environmental conditions that, when applied for a long period, even briefly, would prevent the symptoms of cystic fibrosis from developing even in a child who has two genes for the disease. Wouldn't that be great! After all, the symptoms of phenyl ketonuria can be easily avoided by avoiding specific foods. Also, if you isolate genes and keep them in a test-tube, they will do nothing. They need the internal environment of a living cell in order to function, and that internal environment cannot develop without any effects if the external
[Comment posted 2008-05-13 21:56:56]
I base my explanation of honeybees on published research; unlike yours, which is based on ignorance.
Frankly, you must be a major dolt to post your delusions here without researching for the studies that refute them.
[Comment posted 2008-05-13 18:55:52]
You state that nothing is inherited, if I understand you correctly. So, if your child receives two bad copies of the cystic fibrosis allele, then they will have cystic fibrosis, no matter what the environment, right? Isn't that considered heredity? Maybe I'm not sure what you are trying to say...
[Comment posted 2008-05-13 18:33:30]
If you do not understand that the frozen eggs example leads to the logically inevitable conclusion that the ability of the egg to develop all those traits that you consider "heritable" depends, among others, on inseparable effects of the genes, and the temperature, which is an environmental factor, your problem is obviously much more serious than a mere attention deficit.
I have no idea how you can compare a dead egg to a frozen egg, which is very much alive. I have no idea what makes you believe that the traits of honeybee males & females come from the queen. I have no idea why you are obsessed with religion, and with creationists. And I do not wish to know the explanation to any of these problems you obviously have.
I tried to explain to you a few very elementary things about biology. I did not know at the time that you were a lost case. But I know it now! And I shall never waste any more of my time trying to explain anything to you ever again!
Had I known that your arrogance only fully matches your ignorance, I would not have bothered in the first place.
[Comment posted 2008-05-13 17:02:19]
You make another shallow argument by trying to make a distinction between freezing and killing it ? in both cases all biochemical activity ceases. You?ve yet to present anything substantive that supports your inane assertions. Now you?ve graduated from the trivially obvious to the irrelevant.
Your ignorance of biology runs very deep indeed. Creationists should really research their arguments beyond the websites of the usual suspects; this example of the bee seems so familiar that I suspect it?s lifted from one of those websites. It is nonetheless wrong.
Your very example refutes you ? it shows that traits are indeed heritable and that all the offspring male and female inherit their traits from the queen bee. It seems by your example that that you don?t really understand what inheritance means.
Finally, the workers are not ?manipulating the environment?, the queen manipulates the workers through her pheromones. The absence/reduction in pheromone triggers the workers to select a new queen.
Here are new interrelated concepts to learn: epigenetics, DNA methylation
BTW that?s 3 for 3 in your failure to show that heritable traits do not exist. I suggest you get a bachelors in biology before you go for number 4.
[Comment posted 2008-05-13 13:29:45]
Indeed, I could have killed the zygote, but I deliberately avoided using such a drastic case. I could also have pointed out to you that honeybee queens and workers are all females that develop from fertilized eggs. A queen differs considerably from a worker, (in morphology, anatomy, physiology, and behavior), to the point where you can distinguish between them with one very quick glance. But, when the colony needs a new queen, (because the old one died, or stopped laying eggs), the workers can "manipulate" the environmental conditions to the point of causing one and the same egg, (or very young female larva), that would have otherwise developed into a worker, to develop into a queen!
My argument is trivial only in the sense that it is self-evident, but it is anything but shallow!!! In fact, it is so self-evident, that many, (like you), completely overlook it, just because it is too obvious.
Your problem is that you do not realize the overly obvious, i.e. that learning is just one of many different ways in which the environment can affect ontogeny, (of course invariably, and inseparably from the effects of the genes).
[Comment posted 2008-05-13 05:23:02]
[Comment posted 2008-05-13 05:19:02]
[Comment posted 2008-05-13 04:49:52]
For instance, you can freeze a one-celled fertilized egg, (human, or otherwise), or an egg that has already undergone very few cell-divisions, and irrespective of all the hereditary material it contains, it will never develop any of the individual traits that you label "heritable". To develop any (!) such traits the egg requires, among others (!), a specific, very narrow, temperature-range; which is an environmental factor (!). Moreover, the effects of that environmental factor are inseparable (!) from the effects of the heritable material the egg contains. This is obvious (!) because fertilized eggs of different species may require a very different temperature-range to continue their development.
Mendel never tried anything like that!
[Comment posted 2008-05-12 18:49:59]
[Comment posted 2008-05-10 08:52:27]
[Comment posted 2008-05-09 21:23:51]
[Comment posted 2008-05-09 19:52:46]
In _... Origin ..._, CRD writes about what we now call ecological networks: "It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us." Crucially, what we tend to forget is that every process in/within living systems occurs in a local ecological context.
Fact: all evolution occurs, and has occurred, within a molecular, ecological and/or social network, context or environment. (Challenge: name one biological, psychological or social phenomenon or entity which is not a network or the result of biological network process on one or more length scales.)*
If networks are the fundamental biological unit, they all must share ways of changing (they share a common set of dynamics).* Elsewhere I have proposed six types of dynamics to which all persisting biological networks are subject (there might be others!) and which, in turn, likely produce (most of) the complex phenomena evident in biological process and systems.*
As Professor Greenspan observes, nature is malleable (and, paradoxically, also constant) and we yet evolve (contrary to the dogmatic cornerstone of the evolutionary psychology cult). Immune processes proceed in clearly ecological patterns as do molecular processes in the cell (again, on many length and population-number scales). Too, species consist of similar organisms individually responding to their environment in a physiologically historical context, the molecular dynamics of "homozygous twins" are neither alike nor are the fine-scale molecular residues/substrates of that activity, the genes, exactly alike. Network (species) members (individuals) have to be different in order to provide a complementary function that contributes distinct utility to their network. We each perform distinct roles in our networks of family (several roles!), profession, social group, etc. Competition arises when two individuals' functions are similar.
(I'm responding here to comments made here.) Gehrman rightly observes that "Darwin is underappreciated". True, but part of the reason is that our view of evolution remains incomplete. Notice, as examples, that we have no theory of life -- let alone a definition of the term -- or even a worthy candidate for a unified theory of the life sciences, how molecules --> (have come to make) bigotry, sexual attraction, human economies, universities, authoritarian regimes, etc. Although inchoate, it is clear to many that merely pontificating "genes" or the "survival of the fittest _organism_" fails as an explanation. In my own experience, most reviews of my papers on this topic reveal the reviewers' poor scholarship, particularly on ecological topics (which in my view are the most complex of all biological topics, bewildering and fraught with nuance!). People preferentially absorb, and like to use, simple explanations and buzz words which, even if inaccurate, serve to reassure the speaker that others might infer that they know the topic cold (they are "fit" members of a social network); in truth, NO ONE grasps evolution broadly, and certainly not those who proclaim glibly on those topics.
Andresen bolsters the network view: his parents' fitness acrues in the (social, civilization advancing) network and its likely increased ability to persist under unexpected environmental conditions, although they themselves laudably reproduced relatively less.
Darwin clearly had an inkling of these dynamical relationships and crucial interactions in life's processes. However, he did not posess, and could not access our broadly accumulated and painstakingly refined view of the most complex parts of our universe (much of which can be browsed and sampled from the vantage of an Internet console). Still, without a context of understanding, most such accumulata serves as little more than an awesome collection to the easily impressed (rather than knowledge). We're still at the beginning.
*D. Hollenberg "On the evolution and dynamics of biological networks" _Biology Forum/Revista di Biologia_ 100:1 pp. 93-118 (2007).
[Comment posted 2008-05-09 16:26:18]
[Comment posted 2008-05-09 13:53:56]
Let me use my own story as an example. My parents are professionals and I am an only child with no children of my own; consequently we are not fit. My mother?s water broke long before contractions started, thus she went through induced labor. If this were to happen 60,000 years ago I would have died, and my mother would most likely also die from infection. Although my parents? fitness is low, it is not zero as would be the case 60,000 years ago. This is a simple example, but many other situations are similar: pediatrics departments around the world can tell you the number of children that have been saved and gone on to reproduce; type I diabetes is a perfect example in and of itself.
To conclude, yes humans change (evolve), but is this through a biological natural selection or something more complex?