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Explaining Evolution

AronRa

Administrator
arg-fallbackName="AronRa"/>
Sam said:
Hey Aron, so I was lied to all my life about what being an atheist actually meant, fed falsehoods about knowledge, science, evolution, and the goodness of the Bible. I live in Australia and I've watched a few of your videos; even though my parents weren't religious, my friends and school had some definite overtones of religiosity, so I think that's why I always found the (false) position of the atheist to be so strange and illogical. I feel lied to. I'm doubting the existence of a creator but I don't quite understand evolution. Do you still offer those 1-on-1 'I can prove evolution to your satisfaction' interactions, or was that a long time ago?
I'm still doing those conversations. I'll be happy to explain evolution to you. Let's start by assessing what you know already. So please explain how you think evolution works, and we'll go from there.
 
arg-fallbackName="Canton"/>
Thank you for taking the time to do this.

I've been attempting to digest definitions of evolution and found that yours explains it best: Descent with inherited genetic modification. I had no serious science education after ninth grade due to health complications and a restricted curriculum, so I apologise if I'm a bit basic or illiterate in scientific terms.

What I've been reading over the past few days is that we can all trace our ancestry back throughout time to an ancient earth, where the first cell somehow arose from a process I don't understand. I think people call it abiogenesis. I'm not sure if that's part of evolution, but since it's what kicks it all off allegedly, I'd like to know what happened there. From there, it is my understanding that a small population capable of reproduction began to grow, but I'm confused as to how tiny organisms 'knew' how to reproduce in the first place.

When an organism reproduces, it uses its DNA to produce a copy of that information somehow, but it's imperfect and sometimes gets it wrong, which I think is mutation. Let me know if this is terribly wrong.
 
arg-fallbackName="Sparhafoc"/>
Hi Canton

I'm not Aron Ra, just in case you didn't notice! :) But I thought I'd respond too.

I think you've got the basic gist down.

I think it's probably best not to conceive of the earliest forms of life as being 'organisms' - this word implies a host of functions that there's no reason to assume the earliest life forms would possess, such as reacting to stimuli.

What is absolutely necessarily a function of the earliest life though is 'reproduction' - although replication might be a more informative word. The function of making copies of itself. This wouldn't include any form of knowing, it would have been purely chemically driven. At this point in the development of life, there was no 'reproduction' in the sense of sexual reproduction and the recombining of different DNA, rather it would have been the division of one cell to become two identical cells, and those cells then dividing to become 4 and so on.

I am not sure how familiar you are with these concepts, but I'd suggest you consider the difference between meiosis and mitosis



On to the last sentence: when an organism reproduces (i.e. sexual reproduction), the DNA *is* the information in the sense of it bearing the particular characteristics that form that organism, and the copy process is meiosis which means that one strand of an individual's DNA combines with one strand of another individual's DNA resulting in offspring representing 50% of each parents' DNA.

From an evolutionary perspective, while mitosis is much 'cheaper' and results in identical copies, but if there is a flaw in the original, there's likely a flaw in all offspring... alternatively, if there is an external risk to the parent which impacts that flaw such as a disease, then all the population is at risk of that disease as all share identical (or near identical) DNA. Sex evolved much, much later, and 'solves' or at least lessens the impact of these problems; a flaw in one parent may not transfer into offspring thanks to the combination with the other parents' DNA absent that flaw; similarly, a disease which exploits a particular genetic make-up has less opportunity to infect an entire population when it is comprised of many different genetic combinations.

There are numerous ways in which mutations can arise and they represent one of the primary sources of genetic variation. The example you pointed out is a replication error, and these can take different forms such as deletion (the removal of a stretch of DNA) and insertion (the addition of a stretch of DNA), or stretches of DNA can be 'turned on or off' (inhibited). Copying errors can have no immediate impact, but may offer further or brand new mutations in successive generations.

These kind of mutations are frequently deleterious, meaning that the result is NOT beneficial at all to the organism, perhaps even resulting in the offspring terminating in gestation. A lot of these mutations are neutral - they have no actual impact positive or negative on the survival of the possessing individual. Some few may be beneficial and give the individual some form of advantage - typically very minor, such as a slightly more efficient processing of nutrients for example.

Evolution then is the statistical reshuffling of this genetic variation across multiple generations. New 'information' is continuously being generated and sorted, either through constraining selection forces where the environment interacts with individuals which experience differential survival - a term which also implies 'successful reproduction' - and those qualities are thus retained in future generations, or through genetic drift where no specific variation in a population offers any survival benefits or maluses but still continuously gets reshuffled producing new forms and potential opportunities for new mutations.
 
arg-fallbackName="Canton"/>
Thank you very much for the comprehensive post. I like that website's approach to laying out facts and clearly defining terms. I believe I understood most of that, but I think I'm a bit confused about why cells divide and reproduce to begin with. It's fascinating to think that something purely chemical and largely chaotic would work this way, but I guess that's my lack of biological and chemical education showing through.
 
arg-fallbackName="AronRa"/>
Thank you for taking the time to do this.

I've been attempting to digest definitions of evolution and found that yours explains it best: Descent with inherited genetic modification. I had no serious science education after ninth grade due to health complications and a restricted curriculum, so I apologise if I'm a bit basic or illiterate in scientific terms.

What I've been reading over the past few days is that we can all trace our ancestry back throughout time to an ancient earth, where the first cell somehow arose from a process I don't understand. I think people call it abiogenesis. I'm not sure if that's part of evolution, but since it's what kicks it all off allegedly, I'd like to know what happened there. From there, it is my understanding that a small population capable of reproduction began to grow, but I'm confused as to how tiny organisms 'knew' how to reproduce in the first place.

When an organism reproduces, it uses its DNA to produce a copy of that information somehow, but it's imperfect and sometimes gets it wrong, which I think is mutation. Let me know if this is terribly wrong.
I like to point out that a lot of people are looking for that Last Universal Common Ancestor of all life, usually to link prokaryotes (bacteria/Archaea) and eukaryotes (everything else). I'm not looking for that because there are some uncertain things happening at the base of Eukarya that are not evolutionary processes. There is a lot of horizontal gene transfer happening with unicellular microbes, where bacteria (for example) will exchange DNA on contact. Each of these exchanges likely result in genetic change of a type that doesn't make sense in a phylogeny. Evolution is an ancestor-descendent relationship. So we can't fairly say that we evolved from bacteria. There were other processes going on that are not evolutionary processes.

Another important thing to know is that for sexually-reproductive animals, the parent gene-pool of the surrounding population tends to restrict new variance. Mutations provide new variations, but these don't contribute to evolution until they are shared by a significant population generations later, and most such mutations never make it that far, because of recombination with mates and the 'norm' which typically overrides the new. However, in smaller populations, the dominant gene pool has less restrictive influence. So most new varieties come form isolated strains taken out of the general population.

Beneficial mutations are rare, but often enjoy selective pressure. Deleterious mutations are more common, but they also tend to get weeded out pretty quickly. Most mutations are harmless and neutral, allowing for a vast amount of variety in every direction, which may be the best way to see biodiversity.

I should also say that evolution at every level is usually a matter of incremental, superficial changes being slowly compiled atop successive tiers of fundamental similarity and these tiers of similarity establish taxonomic clades. Every new variant is just a modified version of whatever its parent group was, and it still belongs to every ancestral clade that they did. Evolution never has one "kind" of thing turning into another fundamentally different "kind" like creationists always pretend. That would actually violate two evolutionary laws.
 
arg-fallbackName="Sparhafoc"/>
Thank you very much for the comprehensive post. I like that website's approach to laying out facts and clearly defining terms. I believe I understood most of that, but I think I'm a bit confused about why cells divide and reproduce to begin with. It's fascinating to think that something purely chemical and largely chaotic would work this way, but I guess that's my lack of biological and chemical education showing through.

That's a deeply philosophical question that perhaps no human being could ever hope to answer. 'Why' questions are really important to us - we see cause and effect and thus we attribute the cause as the 'why'. But science does not and cannot really hope to ever satisfy a 'why' question because that necessarily entails an endless iteration of proximate explanations - to fully answer a 'why' question would entail me producing a complete working model of the entire universe and every interaction that ever occurred, and I lack the preponderance of relevant knowledge, and even if I had it, we certainly wouldn't have time to review it! :)

See here a somewhat tetchy, somewhat bemused response from one of the world's great physicists - Richard Feynman - to an interviewer asking a why question...



As unsatisfying as it may be, all cells divide and replicate - that's what a biological cell is; it's definitional. There was never a time when a cell didn't divide and replicate. So there was no notional time prior to the advent of life where cells existed but were yet to 'evolve' the ability to replicate. However, things which aren't cells can replicate such as certain molecules. The transition to what we would identify as life wasn't just replication because chemical replication occurred previously, rather it was the combination of chemical replication with homeostasis - the partition of molecules between an inside and an outside. For example, if RNA can auto-catalyze and produce enzymes that benefit itself, but that RNA is exposed to the outside environment, then the enzymes produced are 'lost' to the wider environment. If there is a partition between that enzyme factory and the outside world, then the enzymes produced are wholly exploitable by the producer of those enzymes. Thus, again definitionally, a cell also necessarily infers a membrane structure which functions to separate the inner from the outer. Again, we see precursors of this for example in proteinoids: https://en.wikipedia.org/wiki/Proteinoid

So prior to life, in the abiotic world, we see plausible examples of existing non-living quantities which possess the functions which life would exploit, rather, the specific set of exploitation of these functions is what we call life.

Why is this? Because that's just how chemistry works in this universe with this set of molecules, and this suite of forces, under these available conditions. It doesn't mean it's guaranteed to happen, or to happen in a specific way, but the why is because it can happen, and given enough time and the right conditions, this is what molecules can do. It happened here, it's entirely plausible it's happened elsewhere, and that life may be very, very different from ours, but presumably shares these basic characteristics of replication and homeostasis.
 
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arg-fallbackName="Canton"/>
Okay, so I've gone a bit nuts watching educational videos and devoured the entirety of the Systematic Classification of Life series you made, Aron, and I can safely say that the real answer to where we came from was far more interesting than I could have even expected it to be. It's awesome. It's so much more satisfying than 'we're here because god and we're very special'. I know we just started this conversation but I honestly believe that evolution no longer needs to be proven to me; it's the answer that all the data leads to, just without human vanity in the way, wanting to make us the star of the show. We are special, but only because we're smart, and we're the survivors of a long, long, amazing chain of life.

And I guess I didn't realise I was asking a philosophical question, but it does make sense now that it's been explained.

I want to thank you Aron for your entire channel, and the new hunger for knowledge I feel. I... have a lot of science to catch up on, it feels like. I'm just grateful that knowledge is so easy and cheap to obtain these days, and that communities dedicated to facts exist with such generosity of time and knowledge. And I'd like to thank you too, Sparhafoc, for that generosity.
 
arg-fallbackName="Sparhafoc"/>
I want to thank you Aron for your entire channel, and the new hunger for knowledge I feel. I... have a lot of science to catch up on, it feels like. I'm just grateful that knowledge is so easy and cheap to obtain these days, and that communities dedicated to facts exist with such generosity of time and knowledge.

You know, you also help so much by asking these questions. People like yourself, with questions that have come to them later in life long after they've ended formal education, make responses to those questions so much more amenable to others in a similar situation. A lot of people may have questions but not necessarily want to watch long instructional videos, or read a complex exposition - they want to ask a straight question and get a straight answer, and they want to know what validates that answer. For me, at their best, that's what forums like this can provide.

For me, the greatest satisfaction I've found in life is the discovery that knowledge is basically fractal. The wider you look, the more things there are to know, whereas the closer you look, the more detail comes into view. Every single discovery raises a hundred new avenues of ignorance which previously were not conceived. Or as Darwin put it: ignorance more frequently begets confidence than does knowledge.

No one person knows or even can know everything, broad or detailed; we're all here to learn! :)
 
arg-fallbackName="AronRa"/>
Okay, so I've gone a bit nuts watching educational videos and devoured the entirety of the Systematic Classification of Life series you made, Aron, and I can safely say that the real answer to where we came from was far more interesting than I could have even expected it to be. It's awesome. It's so much more satisfying than 'we're here because god and we're very special'. I know we just started this conversation but I honestly believe that evolution no longer needs to be proven to me; it's the answer that all the data leads to, just without human vanity in the way, wanting to make us the star of the show. We are special, but only because we're smart, and we're the survivors of a long, long, amazing chain of life.

And I guess I didn't realise I was asking a philosophical question, but it does make sense now that it's been explained.

I want to thank you Aron for your entire channel, and the new hunger for knowledge I feel. I... have a lot of science to catch up on, it feels like. I'm just grateful that knowledge is so easy and cheap to obtain these days, and that communities dedicated to facts exist with such generosity of time and knowledge. And I'd like to thank you too, Sparhafoc, for that generosity.
You are most welcome. :)
 
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