Evolution, the Brittanica.com article: is anyone here..?

  • #1

Main Question or Discussion Point

Is anyone here familiar with the Brittanica.com article on evolution? I was just about to read it but had a quick look at the article history to see if it was by a scientist or just one of the Brittanica editors. It is by a scientist but one who's won the Templeton Prize and written a books called, "Am I a monkey?" and "Darwin's gift to science and religion." This gave me pause for thought recalling Richard Dawkins scepticism of scientists who lower themselves (as he sees it) by accepting the Templeton Prize.
Also, can anyone recommend a solid but accessible for beginners article/site on evolution?
 

Answers and Replies

  • #2
Bandersnatch
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I've just read the first half of the article, and only skimmed over the second part (it's a venerable wall of text). I think it's sound. There is no fundamentalist religious bent to it that I can see, and it's quite thorough - especially in matters of history and cultural context. The second part seems to focus on more technical aspects, but as mentioned, I haven't read it in detail.
The author spends quite a bit of time discussing various aspects of opposition to evolution, and does so very matter-of-factly, in a considerate and careful manner. At no point in doing so does he cast doubt the merits of the theory, attempt to put it on equal footing with creationism, or smuggle any other unsavoury messages.

The guy's no creationist, nor does he have much love for them as can be hinted from bits such as this one:
For skeptical contemporaries of Darwin, themissing link—the absence of any known transitional form between apes and humans—was a battle cry, as it remained for uninformed people afterward.
If I were to guess, and judging by this piece only, I'd say his Templeton Foundation prize recognizes that he writes about subjects such as these by clearly placing them in a cultural context digestible to (rational) people of faith, without derision.

If I were a reader of religious provenance unsure what to think about the whole issue, this kind of an article would have much higher chance of dispelling any doubts I could have had accrued w/r to science, than Dawkins' cheeky aloofness - which, while entertaining to some, might offend others.
It's also a good article for somebody wanting to learn what the whole modern controversy is all about, or who wants to have the full picture including the history.

For people who don't care much for historical context or clashes with creationism, and want to know just about the particulars of the science, a more trimmed and/or technical article would probably be better. I think Wikipedia's is quite good in this respect.
 
  • #3
Thank you, Bandersnatch, I've made a start on it and finding it an enjoyable read so far (I particularly enjoyed finding out that sequoias can grow to 300ft). I'm not sure about the significance of our genetic similarity to other organisms though (from other articles, not this one). I've read we're 99.9% genetically similar to each other which seems to me to make sense given our obvious anatomical and physiological similarities but when I read that we're 96% genetically similar to chimps; 90% to cats; 85% to mice; 80% to mice; 60% to chickens; and 60% also to bananas it struck me that we don't seem to be 96% similar to chimps in anatomy or physiology, and we're clearly not 60% similar in these respects to bananas. This leaves me wondering if the significance of genetic similarity has been exaggerated.
 
  • #4
Bandersnatch
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it struck me that we don't seem to be 96% similar to chimps in anatomy or physiology
What organs, body parts, cell types, synthesised molecules or intracellular chemical processes are qualitatively different? If you were to list all the instructions that are need to be encoded to make a hominid from a single fertilised cell, down to all the smallest and most fundamental building blocks, what proportion would be made of simple changes like making this or that characteristic larger or smaller (e.g. bigger cerebellum, less hair, shorter arms, more neurons, etc)?

Similarly with bananas. There is a whole ocean of internal chemistry that governs the basic structures that is the same. You can arrange those building blocks in wholly different ways. It's like design papers for making a LEGO castle vs a LEGO spaceship. The instructions for the end-user is just one sheet of paper with colourful pictures. The instructions for how to make the blocks in a factory from raw materials is a heavy brick of design documents that is essentially the same for all sets of blocks.

Since we normally don't get to see anything but the superficial structure, we tend to think that it's all there is.
 
  • #5
BillTre
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I'm not sure about the significance of our genetic similarity to other organisms though (from other articles, not this one). I've read we're 99.9% genetically similar to each other which seems to me to make sense given our obvious anatomical and physiological similarities but when I read that we're 96% genetically similar to chimps; 90% to cats; 85% to mice; 80% to mice; 60% to chickens; and 60% also to bananas it struck me that we don't seem to be 96% similar to chimps in anatomy or physiology, and we're clearly not 60% similar in these respects to bananas. This leaves me wondering if the significance of genetic similarity has been exaggerated.
The significance of genetic similarity (similarity of their genomic sequences or maybe just the sequences of genes) should be most directly related to how closely related the different organisms are.
This can be thought of as for how long have they been evolving their own separate directions since they last had a common ancestor. the last common ancestor would be the deepest branch point in a phylogenetic tree that separates two species. This can be approximated from the genome differences (in a complex manner) and these dates can be calibrated (rates of evolution can vary among different species) based on dates of fossils of last common ancestors.
Some of the sequences will be conserved for functional reasons, but others will be free to vary and can slowly change over time. The proportions of the conserved sequences vs. those that change more freely will vary based upon what sequence information they used to generate the percentages (for example total genome sequences will have a lot of sequences that change a lot, but sequences that are part of protein encoding genes will be much more conserved and have fewer sequences that change a lot.

The numbers you cited kind of go along with this but there are some discrepancies. (I have not read your article to check these numbers or exactly how they were derived).
Your numbers show human are closest to chimps, then next closest to cat, then to mice (twice in your list), then to chickens which are tied with bananas.
The commonly accepted evolutionary relationships would have the order as: humans closest to chimps, then mice (rodents), then to cat (carnivora), then to chickens (birds or aves), then bananas (plants).
However, mice (rodents) are more closely related to humans than cats (carnivores), so that seems wrong, and birds are way more closely related to humans (and all animals) than bananas (plants).
So something seems wrong there. Don't know what.

More directly dealing with your question:
There should be a relationship between genetic similarity and anatomy and physiology but it is indirect.
The genome sequences are most directly related to RNAs and proteins that they encode.
The physiological and anatomical features you look at are (in most cases) only indirectly related to genome sequences their directly generated products (RNAs and proteins).
In most cases, anatomical features are produced through developmental processes that involve interaction between large numbers of cells each of which use large numbers of different RNAs and proteins. These interactions, which can have multiple steps, generate the adult structures people most often think about when comparing different organisms. Therefore, the structures similarities will relate to the genetic similarity, but not in a simple manner. The underlying developmental processes will be more directly related to the genetics, but they are less easily compared (requires studying the their embryology or for comparisons studying comparative embryology) and have many molecular components.

Another way to to think about these relationships to consider what two genomes share in their abilities to do different biological tasks. That is, what sets of genes they have that can work together to accomplish a task. The tasks can often be kind of obscure cellular functions that can be used (or re-utilized) in many different developmental or physiological processes.
This can be discussed as the different kinds of molecular or genetic toolkits that organisms share.
Here is a wikipedia article on toolkits of genes for development for example. Here is a shorter article on the same kind of thing.

The gene toolkit idea can also be used with more basic biolgical properties, such as the properties of eukaroytic cells which are very different from bacteria-like cells that preceded them. They would have genes for lots of functions bacteria don't have: a nucleus, mitosis and meiosis cell division, cytoskeletal proteins, proteins to control membrane differences and movements, and more (which bacteria like cells lack. There would be a lot of these genes.
All of them would be (largely) shared among most eukaryotes, including animals, plants, fungi (including mushrooms and yeast), as well as single celled eukaryotes like amoebas and paramecia.

Multicellular organisms (plants, animals, and large fungi) would have additional sets of genes to regulate how the different cell interact to stay together and function as a unit (or to do development).
Since multicellularity evolved after they plants, animals and fungi separated, these sets could be independently derived and different.

All of these different relationships could influence the percentage similarity of the organism's genetics.
 
  • #6
Apes, according to Brittanica (elsewhere in Brittanica, i.e, not in this article); gibbons; orangutans; gorillas; chimps; bonobos; humans.

“The oldest known fossil hominins [tribe] — i.e., primates belonging to the human lineage after it separated from lineages going to the apes — are 6 million to 7 million years old, come from Africa”

Q. Re ‘lineages going to the apes’; According to Brittanica as stated above humans are apes; are we?

Q. Is the above implying that around 6-7 million years ago there was a divergence and that one branch forked into two, one branch becoming the human lineage, one branch becoming the ape lineage? If so, does that contradict Brittanica saying elsewhere that we are apes?
 
  • #7
jim mcnamara
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I am going to try to distill this down to something easier to work with.

You are making this too hard. IMO. You seem to want to assign precise facts to a set of very complex circumstances. Evidence we have for this just starting to emerge in more traditional Paleontology.

Our very best path is to consult our DNA:

https://news.nationalgeographic.com/news/2005/08/0831_050831_chimp_genes.html

This says humans and chimps: 96% of their DNA is the same.

So, apes and humans share a common ancestor. Period. No exclusions. No doubts about common ancestry. This one is simple to see.

Who became what, and when did this happen are debated. Which does not detract from the DNA evidence. Britannica is trying to be precise, perhaps using older information. The first human lineage that became us was probably 7 million years ago. As a reasonable estimate based on DNA comparison between modern humans and anthropoid apes.

So other things are fuzzier with regard to some interesting details - the who, what, and when part, again. Even using DNA.
Why is that? Well, some facts that are clear

1. Millions of years ago there were a lot human-like species wandering around Africa on two legs. With names like Australopithecus or Paranthropus. Early humans appeared in this mix of species. As did modern humans later on.

2. As recently as 30000 years ago other human species lived on an island, and some others lived 200000 years ago in South Africa.
Both with modern humans for neighbors. Homo florisiensis and Homo naledi. If you met one of these guys walking in the park, you would think they looked really odd.

3. From Africa, modern humans moved into Europe, and bred with another human species that was already there, Neanderthal. Give a Neanderthal a bath, a shave, and a haircut, then put him on the rush hour bus. He'd fit right in. Plus if your background is European, you have Neandertal DNA ~4%. So they bred with the newcomer humans.

4. Early modern humans moved into Asia. If you have Asian forefathers, then you have about 2% DNA from another species of human, Denisovan. Denisovans were already there in Asia first, like Neanderthals in Europe. And they bred with the new humans coming in, too.


What does this mean? Other human species were around at overlapping times with our ancestry in the past. Sometimes swapped DNA with our distant ancestors..

Precisely when and what humans are is not cut and dried. And not as precise as presented sometimes. I hope this helps.
 
  • #8
BillTre
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They should have included a phylogenetic tree of some kind. It makes these relationships easier to understand.
Here is a evolutionary tree from a wikipedia article.
700px-Hominidae_chart.svg.png

Lineages are like the lines connecting the different parts of the tree, leading to different results.
Most taxonomic units are now applied to naming clades, groups of species that include all the descendants of a particular branch point in the tree.
The clade names in the diagram are at the branch points of the lineage leading to humans in the tree. The yellow Hominidae is one of them.
By this logic, humans (in the genus Homo) are members of all of the following groups: Hominini, Homininae, Hominidae, and Hominoidea (going from smallest groups to the largest groups).
By the naming logic of the diagram, humans would not be members of Pan, Gorillini, Ponginae, or Hylobatidae.
These are separate groups that originated (became their own clades, made new species (such as speciating different gorilla species), etc.) after becoming evolutionarially separate from the lineage leading to humans.

To answer one of your questions (are we classified as apes), it depends what you call apes.
If it refers to one of the names on the lineage in the diagram leading to Homo, then yes.
If it one of the other names, then no.
 

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  • #9
Laroxe
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I was thinking about the idea of genetic similarity when species are so different. In fact the current ideas about how genes work are becoming much more flexible and nature certainly has a habit of re purposing existing structures rather than re inventing things. It seems the presence of individual genes doesn't tell us much, genes operate in associated networks and the way these interact and the timing of gene expression is what makes the differences. It also seems to be the case that the idea of a single gene coding a single protein isn't accurate its becoming increasingly clear that a single gene can code for multiple proteins. I think the record is held by a fruit fly gene that has been associated with over 200 protein products.
https://science-explained.com/theory/one-gene-many-proteins-alternative-splicing/
 

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