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Author Topic:   Who Owns the Standard Definition of Evolution
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003


(2)
Message 334 of 697 (915275)
02-12-2024 9:29 AM
Reply to: Message 12 by K.Rose
02-06-2024 5:39 PM


One of my undergraduate textbooks says this:
Evolution in the process of biological change by means of which different types of organisms have inhabited the Earth at different times. A common definition used by biologists is 'any cumulative change in the heritable characteristics of species or populations from generation to generation, or over longer periods. Darwin used the wonderful succinct phrase 'descent with modification': descent from an ancestor and modification of biological features with time.
Which is about as good a definition as you will find. Probably it will not satisfy you, and it certainly isn't handed out from on high by some authority. It's just what the team writing that book agreed on.
So let me ask you why you think there should there be a definition of evolution? And why would there be an "authority" approving such a definition? Who would want this, and why? Who would such a definition be for? Scientists don't need it for anything.
I suspect that what you are thinking of as "evolution" is actually the wide range of varied theories, hypotheses, and facts that collectively form the broad fields of evolutionary research, genetics, and palaeontology - and many others beside. Evolution is still a field of active research with many details still be discovered, and with many details over which current opinion is divided.

This message is a reply to:
 Message 12 by K.Rose, posted 02-06-2024 5:39 PM K.Rose has replied

Replies to this message:
 Message 364 by K.Rose, posted 02-12-2024 8:04 PM Dr Jack has replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003


(4)
Message 386 of 697 (915367)
02-13-2024 4:53 AM
Reply to: Message 364 by K.Rose
02-12-2024 8:04 PM


It has been a very long time indeed since I was taught evolution in school, and I don't remember in any great detail what exactly we were presented with. But it seems unreasonable to me to expect the simplified version of evolutionary theory presented to children to be an exact match to the real and messy world of scientific research. I do remember that when I was first taught about the structure of atoms we were shown an image that looked a bit like this:
Showing Bohr's "solar system" model of an atom, in this case Carbon-12. This is known to be wrong. It has been known to be wrong for a very long time, but the real structure of the atom is far too complex for an introductory class and only the most basic elements of it are taught before undergraduate level classes. In mathematics I remember first being taught division-with-remainder, then fractions, then decimal notation; and I remember that we were taught that one could not take the square root of a negative number before learning at 17 how to handle imaginary and complex numbers. Education proceeds from simpler versions to more complex, with the details necessary to start real scientific research taught only at university level (and beyond).
I think Zallinger's "March of Progress" in its original form is a wonderful illustration of what was known about Human evolution at the time that it was drawn with the simplification necessary for a non-scientific audience. But, I also agree with the many evolutionary scientists who have long argued that it is too simplistic and gives the unfortunate impression of evolution as a directed process akin the medieval idea of the great chain of being.
I am rambling, let me come to my point.
The aim of school education in science is mostly to give students a very basic grounding in the major ideas and topics that are important. It is not to convey the complicated details, nor to communicate everything that is necessary to demonstrate the truth of what is conveyed. This, unfortunately in my view, tends to leave students with the impression that science is a body of facts to be learnt rather than a process for understanding the world. Scientific communication, such as the text for which the "March of Progress" was drawn is also aiming to communicate findings in a way intelligible for a lay audience.
What you have been presented with is not the vast body of evolutionary research, but rather the simplified version for children. Just as the solar system model of the atom is not quantum mechanics, the "March of Progress" is not evolutionary theory.

This message is a reply to:
 Message 364 by K.Rose, posted 02-12-2024 8:04 PM K.Rose has replied

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003


(1)
Message 477 of 697 (915651)
02-16-2024 5:03 AM
Reply to: Message 464 by K.Rose
02-15-2024 4:35 PM


Well, M and N are both modern humans so come from populations that could interbreed. J-L are Neanderthals, labelled there as H. sapiens neanderthalensis (i.e. as a subspecies of modern humans), but more commonly styled as H. neanderthalensis, and we know that modern humans carry some Neanderthal derived DNA so they probably could.
A is a modern chimp, and there are no known human-chimp hybrids so it seems highly likely to be impossible.
As for the rest, how would we ever test it? We could guess that the fusion event in the human chromosome that is estimated to have occurred 0.4-1.5 million years ago forms an absolute barrier between species with 46 chromosomes (us) and 48 chromosomes (as is the ancestral state of the great apes and retained in chimps and gorillas). Which would mean that B-H are excluded from the group that includes us and Neanderthals. For I (H. heidelbergensis) we have no evidence for the chromosomal state of H. heidelbergensis so it may have retained the ancestral state and it may not and even if it carries the same chromosomal fusion that isn't sufficient to imply they could interbreed.
Perhaps the more important question is why you think that whether they could interbreed or not is important?

This message is a reply to:
 Message 464 by K.Rose, posted 02-15-2024 4:35 PM K.Rose has replied

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 Message 483 by dwise1, posted 02-16-2024 12:49 PM Dr Jack has not replied
 Message 499 by K.Rose, posted 02-17-2024 12:31 PM Dr Jack has replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003


(2)
Message 531 of 697 (915896)
02-20-2024 4:42 AM
Reply to: Message 499 by K.Rose
02-17-2024 12:31 PM


K.Rose writes:
The outward implication is that A eventually became N. I am trying to understand how this diagram shows us when one species/kind/lifeform evolved from one to the next, if its purpose is to demonstrate common ancestry.
Hmm, yes, I can see that this is the obvious take from it. That's unfortunate, because N did not evolve from A. Here A is a modern Chimpanzee skull, but humans did not evolve from Chimpanzees instead humans and Chimpanzees share a common ancestor from which they have both diverged for roughly the last 6 million years and modern Chimps have also diverged from that ancestor. We don't, unfortunately, have many skeletal remains that are clearly linked to chimpanzee evolution. But something like Sahelanthropus tchadensis would be closer to our common ancestor with chimps, with scientists still debating whether these species are related to the human line or not.
What the diagram is supposed to show is how the fossil record shows the existence of extinct intermediaries that link H. sapiens to other living great apes. We see, over time, the accumulation of the distinct differences that humans have compared to other apes - most of these, of course, are found below the neck in the structure of the hands, pelvis, legs, and feet. Although the skulls too, if you were able to examine them closely, show the telltale signs of bipedalism.
K.Rose writes:
Also, N is chosen as representative for modern, contrasting sharply with J,K,L,M. Everyday I can see live humans whose skull shape more closely resembles J,K,L,M than N, mine included.
While you might think that this from a glance as a small photo in a diagram such as this, were you able to more closely examine the skulls J, K, and L you would immediately recognise features that distinguish these from M and all modern humans. Most obviously the shape of the skull is much flatter and elongated than any modern human, they also lack the more globular cranial covering of modern human, their brow ridge is far more prominent than even the most dramatic of modern humans, and were you to flip the skulls over you'd note the markedly distinct incisors and a number of more technical differences in the other teeth.
K.Rose writes:
If it was possible for J,K,L,M,N to interbreed, what's to prove that these are not just a variety of different humans.
If potential interbreeding is indeterminate, then how is this uncertainty reflected in the conclusions?
I'm afraid I remain unclear why you think a theoretical potential for interbreeding is important? So I must ask you again to elaborate on this point? We can certainly be sure that D-E did not interbreed with modern humans due to the gulf of time separating them, just as we can be sure that Abraham Lincoln has no children with Marilyn Monroe because they lived at different times. So I'm not sure why the question of whether they could have interbred if that were not so is important?

This message is a reply to:
 Message 499 by K.Rose, posted 02-17-2024 12:31 PM K.Rose has not replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003


Message 555 of 697 (915965)
02-21-2024 8:01 AM
Reply to: Message 554 by Percy
02-21-2024 6:49 AM


Percy writes:
I thought he was charming but my girlfriend couldn't stand him because he would drop in occasional comments like, "But we should get together later and discuss this, girls. But don't worry, I'm not virile." She found him too dirty-old-manish.
Asimov was a famous creep, noted for groping women. It was so well known about him that he was once jokingly invited to give a talk on "The Positive Power of Posterior Pinching".

This message is a reply to:
 Message 554 by Percy, posted 02-21-2024 6:49 AM Percy has not replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003


(2)
Message 561 of 697 (915984)
02-21-2024 1:35 PM
Reply to: Message 504 by K.Rose
02-17-2024 1:19 PM


K.Rose writes:
In a nutshell then, we assume that the present results from the past, without fully understanding the process in between, and then apply present processes to explain the past, such that it fits our theory of the process in between.
But this isn't what happened. Rather than assuming that the present results from the past, scientists gradually figured out how the processes of the present gave rise to what they discovered about the past.
Go back to the start of the 17th century and the prevailing view was that the world was unchanging, but as people began to develop the science of geology they discovered that the layers of the Earth occurred in predictable orders and these layers could be identified by characteristic fossils within them. At the time, people still believed that fossils were spontaneously generated within the ground rather than being the remains of long dead animals.
The chap who figured out what they actually were was one Nicholas Steno, who looked a bit like this portrait, painted many years after his death:
Incidentally, you might immediately notice the prominent cross hanging about his neck - that's because he went on to become a bishop after his groundbreaking (literally!) geological work. His seminal 1669 work De solido intra solidum naturaliter contento dissertationis prodromus (that's Preliminary discourse to a dissertation on a solid body naturally contained within a solid in English, gotta love old book titles!) laid down four principles about stratigraphy that are still basically held to today:
  1. The Law of Superposition: which states that, in an undisturbed sequence, the oldest strata (that's the technical word for the layers that the Earth is composed of) are found at the bottom of the stack.
  2. The Principle of Original Horizontality: which states that each stratum was horizontal when first formed.
  3. The Principle of Lateral Continuity: which states that each stratum must have had something that bounded it, or covered the entire Earth.
  4. The Principle of Cross-Cutting Relationships: which states that if a body or discontinuity cuts across a stratum then it must have been formed after the stratum.
It didn't take long for these ideas to become widely accepted, not because they are based upon some assumption but because they match very well indeed with what can be observed in the world, and because they make simple logical sense.
Of course, people still believed that all this was the result of God's creation, perhaps best expressed by William Whiston's A New Theory of the Earth, published in 1696, which described at length how all that was described in the Creation accounts in Genesis matched with what was observed in the geological record. Over time more and more details of geology were figured out by a procession of scientists over the following decades and centuries. Don't worry, I shan't attempt to enumerate them all here, just pick out a few key players.
The next is Abraham Gottlob Werner, a German geologist who did fantastic work in creating detailed records of the rocks across Europe, and for some dramatically wrong theories about how they formed ("Neptunism" which posited that basalts precipitated out of a global ocean). All this work on rocks, by the way, was of huge interest to people of the time because understanding the stratigraphy of a region allows the successful prediction of where coal deposits can and can't be found - something of great interest to the industrialists of the era. This is something that only works because these layers were laid down in order over time, and because the coal deposits of the world nearly all date to a single 60 million year period of the Earth's history (the Carboniferous) which marks the period between when trees first evolved and when fungi capable of efficiently digesting lignin evolved. This means that if you know that the surface rocks of the world are older than the Carboniferous you won't find coal beneath them.
The idea that the past can be explained by invoking present processes didn't obtain popularity until one James Hutton entered the scene, a Scottish polymath, his studies of the geology and geography of Scotland led to him developing his theory of uniformitarianism, published in his 1785 work Theory of the Earth which posited that the Earth had been around for vastly longer than was supposed by people of the time. Hutton, incidentally, believed that the Earth was being maintained in a state suitable for humans by a divine power. Bit-by-bit, Hutton's theory of geology, based primarily on volcanic activity and erosion (aka "Plutonism") gradually pushed out Neptunism as the evidence for it was much stronger.
By this time it was obvious to anyone who had studied the geological record that the animals present in the earliest strata were quite different from the animals of the present day and to the animals to the many other strata in between. But in contrast to Lamarck, a man named Georges Cuvier believed that rather than showing change between forms (evolution) than these different animals were different epochs of life separated from each other by vast catastrophes, and rather than the strata representing the slow action of time - as per Hutton - he believed that they were primarily formed in these catastrophes.
At last, in 1830, we come to Charles Lyell's Principles of Geology, which outlines in painstaking detail how the geology of the past could be explained by the slow action of processes that can still be observed today finally did for Cuvier's theory of Catastrophism. I have a later edition sitting on the shelf to my right, along with his rather more accessible Student's Elements of Geology, and it really is striking how much of what he wrote still stands up today, as does his pithy statement that "the present is the key to the past".
Well over a century of research, careful observation, and passionate debate led to that conclusion, and it would be some decades more before Lyell was universally accepted. It wasn't an assumption, it was the result of painstaking observation.
And it's that same painstaking observation that lead to the recognition of the times that uniformitarianism is not true, such as when a comet struck the Earth around 65 million years ago, and led to the extinction of all the non-avian dinosaurs. Again, not assumption, observation.

This message is a reply to:
 Message 504 by K.Rose, posted 02-17-2024 1:19 PM K.Rose has not replied

  
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