Evolution Help?

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Adam Preston
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Evolution Help?

Postby Adam Preston » Mon Oct 31, 2011 9:17 pm UTC

Ok, so we all know that there existed cells as single cells first of all but then we began seeing multicells, I'm simply curious why they began becoming multicelluar, is it to improve their chances of survival? Also, while thinking about how complicated our bodies are, is it really possible that this incredibly complicated organism was created by chance because of many many years of evolution or intelligent design of a creator? Because I simply don't see why cells would exist purely in the body for one function, is this simply so they can survive better? I'm probably unclear in what I'm asking so please ask if you don't understand something I've said.
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Re: Evolution Help?

Postby Gigano » Mon Oct 31, 2011 9:46 pm UTC

In essence you are looking for the reasons why tissues and organs exist, and the answer to that has already been given by you: it indeed helps to promote survival. But more interestingly, why does grouping together promote survival? Imagine a single hunter/gatherer looking for food by his own, and imagine a large group of hunter gatherers doing the same thing together. Whom you think would have the better odds of survival? The group of hunters is more likely to finding a decent quantity of food to sustain their group than a single gatherer would. Delegating various tasks to various individuals (i.e. specialising in scouting, running, killing etc.) also helps to optimise the efficiency of a group. You could also look a colony of bees. Who in the colonies gets to reproduce and pass over the genes to the next generation? The queen does; all the other worker bees and drones serve to supply the queen with nutrients and a safe place to reproduce. You may think it odd that all the other bees, apart from the queen, exist solely for one function which doesn't even include reproducing themselves, but evolution doesn't really care in that sense: whatever inherently helps the survival and continuation of genes is going to become a dominant strategy at some point.

There is a beautiful example of a very simple kind of multicellular organism, existing of just a single cell type, and it's called Volvox. It's a genus of algae that forms spherical colonies. All the cells work together to produce food for the good of the colony. There is also a very simple example for animal cells functioning together in a simple kind of tissue, and you may have heard of it: sponges. Sponges contain just a couple type of cells ranging from structural cells to a very simple immune system. They all serve to ensure optimal odds of survival and reproduction of the main organism. In the same way, we humans are a collection of various specialised cells that all work together in order to survive and reproduce. A Dutch neurobiologist, Dick Swaab, once even mentioned a brian-centric view of the human body, that is "the human body serves to supply the brain with oxygen, nutrients etc. in order to produce more brains".

So a shorter version of the answer is that specialisation into various tissues helps to optimise certain biological functions that help to promote survival and reproduction. I could also go into to details about the mechanisms by which tissue and organ specialisation evolved, but there is plenty of solid information on that topic available in books and on the internet.
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Re: Evolution Help?

Postby scarecrovv » Mon Oct 31, 2011 10:12 pm UTC

Adam Preston wrote:I'm probably unclear in what I'm asking so please ask if you don't understand something I've said.

You're right. It's not clear what you're trying to ask. I'll try though.

Adam Preston wrote:Ok, so we all know that there existed cells as single cells first of all but then we began seeing multicells, I'm simply curious why they began becoming multicelluar, is it to improve their chances of survival?

Yes. I am not a biologist, but as far as I understand, single celled organisms initially found it useful to communicate with each-other, and developed mechanisms for doing this. The benefits of communication are obvious. For example, if one organism detects some dangerous condition, it can alert all its neighbors, so they can prepare. Over time, intercellular cooperation became more intricate, eventually resulting in diversified cell types for performing specialized tasks, and then multicellular organisms.

Adam Preston wrote:Also, while thinking about how complicated our bodies are, is it really possible that this incredibly complicated organism was created by chance because of many many years of evolution or intelligent design of a creator?

This is a complicated sentence, with several claims embedded in it.
  • "created by chance" is a very poor description of evolution, because the word "chance" carries many assumptions with it that don't apply in this case. Each individual small step along the path of evolution is taken by chance. However, many of those steps are immediately quashed. Over time, an evolving population of organisms tries zillions of variations of it's current pattern. Most of those variations die out, but the ones that happen to benefit the organisms persist, resulting in the pattern for the organisms changing.

    Here's an analogy: suppose you are trying to reach a specific place, out in the woods. It is dark out, so navigation is difficult. You have two possible strategies for reaching your destination. You could parachute into the woods in a random location, check if you're at your destination, and if not get extracted by helicopter and try again. This is inefficient, is highly unlikely to get you where you need to go, and is what people think of when they say "created by chance". Alternatively you could go into the woods with a cheap GPS that just says "warmer" or "colder" as you get closer or further from your destination, and then walk around. Each step is in a random direction. However, whenever you take a step and the GPS says "colder", you immediately step back. By this process, even though your individual steps are random, they have a bias towards your destination, which you will eventually reach. This is much more like evolution. The difference is that evolution doesn't have a specific goal in mind, certain regions of the woods are just warmer or colder than others, the warm and cold regions move about over time, and there are many, many, people walking about in the woods.
  • "incredibly complicated" is actually evidence for origin by natural processes, and against some intelligent designer. To see why, consider two walls. One is made of driftwood. It is incredibly complicated. Each individual stick is oriented at a different angle, is a different size, a different shape, and there are all sorts of types of wood, some sticks are old, and some are new. It's an incredible hodgepodge. The other wall is made of bricks. Each brick is the same size. The bricks are lined up in neat rows. The spacing between the bricks is the same. The design of the wall is quite simple. Interestingly, the simple wall was designed by an intelligence, and the complex one was made by waves on a beach. Simplicity is a hallmark of intelligent design. This is something we do not observe in nature.

Adam Preston wrote:Because I simply don't see why cells would exist purely in the body for one function, is this simply so they can survive better?

Yes. If a cell carries out one function, and only one function, it can be very good at that function. This is the same reason we have civilization, with each person having a different job. We can survive better that way, as a group.

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Re: Evolution Help?

Postby Izawwlgood » Mon Oct 31, 2011 10:36 pm UTC

Thankfully, there are intermediary multicellular organisms!
The idea isn't 'one day there was unicellular organisms in the broth, and suddenly (LE GASP!) you had plants and animals. Multicellular organisms started as unicellular organisms that lived communally, and gradually, tissue specification began.

And basically as for why cells in a multicellular organism would give up their ability to pass on their own DNA; it's because your nerve cells, say, share way more in common genetically with your sperm cells than your nerve cells do with, say, some random persons nerve cells. The idea being that by better enabling the body as a whole to reproduce, individual cells giving up their own reproductive potential still improve the chance of their own DNA being in the next generation.

This is also true sometimes on the whole organism level; eusocial insects for example, and hell, caring for siblings offspring.
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Re: Evolution Help?

Postby Copper Bezel » Tue Nov 01, 2011 5:50 am UTC

I'm simply curious why they began becoming multicelluar, is it to improve their chances of survival?

I know this has already been alluded to, but I can't not make this explicit, as with every discussion of natural selection - species didn't begin becoming multicellular to improve their chances of survival. Some of them became multicellular (in a rudimentary way,) and it did improve their chances of survival, so that trait spread.
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Re: Evolution Help?

Postby scarecrovv » Tue Nov 01, 2011 3:48 pm UTC

Copper Bezel wrote:I know this has already been alluded to, but I can't not make this explicit, as with every discussion of natural selection - species didn't begin becoming multicellular to improve their chances of survival. Some of them became multicellular (in a rudimentary way,) and it did improve their chances of survival, so that trait spread.

Yes. Right. That is an important distinction. Words are tricky. Thank you.

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Re: Evolution Help?

Postby Adam Preston » Tue Nov 01, 2011 10:16 pm UTC

Thanks very much guys, so multicellular organisms came into existence simply to improve their chances of survival of cooperating so that part of their genome still gets passed on. And to a post before, when I meant chance I simply meant are human being simply this intelligent and complicated because of chance and not "destiny" or religion, couldn't our existence simply have occurred the same way for any other organism under the right circumstances? For example if another species of primate became under pressure of threat from larger predators, they could have perhaps evolved larger brains?
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Re: Evolution Help?

Postby Izawwlgood » Tue Nov 01, 2011 10:23 pm UTC

Sure. There are lots of theories as to why our particular branch developed the intelligence that we did, and at one point in time, there were more than one 'intelligent apes' walking around. But keep in mind we aren't the 'top' of a particular evolutionary tree. We aren't 'better' than chimps or apes. We simply represent different branches off a common ancestor.
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Re: Evolution Help?

Postby qetzal » Wed Nov 02, 2011 1:01 am UTC

Adam Preston wrote:Thanks very much guys, so multicellular organisms came into existence simply to improve their chances of survival of cooperating so that part of their genome still gets passed on.


Not quite. They didn't come into existence for the purpose of improved survival. They came into existence and experienced improved survival. Thus, their lineage continued. Further increases in multicellularity and organismal complexity happened, and also experienced improved survival. Etc.

New traits don't appear because there's some available benefit. They appear, and IF it turns out they provide benefit, they persist. If they don't provide benefit, they don't persist.

(Actually it's more complicated. E.g., even new traits that do provide benefit don't always persist. They may die out just by chance. Similarly, even traits that provide a net detriment can sometimes persist, again by chance.)

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Re: Evolution Help?

Postby Gigano » Wed Nov 02, 2011 4:37 pm UTC

qetzal wrote:(Actually it's more complicated. E.g., even new traits that do provide benefit don't always persist. They may die out just by chance. Similarly, even traits that provide a net detriment can sometimes persist, again by chance.)


Detrimental traits may even persist without chance being involved. For example traits that provide benefit early in life but are detrimental later in life, are selected for and persist in the lineage. This is an example of what is known as antagonistic pleiotropy, and it's related to theories concerning senescence. Just thought it'd be interesting to mention this, though.
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Re: Evolution Help?

Postby gmalivuk » Wed Nov 02, 2011 7:56 pm UTC

Yeah, there's not much selection pressure against traits that kill you only after you've reproduced.
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Re: Evolution Help?

Postby Angua » Wed Nov 02, 2011 11:48 pm UTC

Huntington's is the classic example if you want to look that sort of thing up.
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Re: Evolution Help?

Postby scarecrovv » Thu Nov 03, 2011 5:03 am UTC

Angua wrote:Huntington's is the classic example if you want to look that sort of thing up.

That, and old age.

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Re: Evolution Help?

Postby Gigano » Thu Nov 03, 2011 7:23 am UTC

There is also a nice example in the fish species X. cortezi. In this species there are two two phenotypes of 'spottedness' on the tail fin: very spotted (Spotted Caudal, Sc) and not so spotted (wildtype). The extra spottedness of Sc provides great benefit early in life as females are very attracted to a very spotted look over a not so spotted look. So fish with the Sc phenotype have more success in reproduction. However, the Sc phenotype is accompanied by early melanomas later in life, and so the fish die fairly early compared to the wildtype.
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Re: Evolution Help?

Postby tomandlu » Thu Nov 03, 2011 1:41 pm UTC

gmalivuk wrote:Yeah, there's not much selection pressure against traits that kill you only after you've reproduced.


Hence the existence of mother in laws...
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Re: Evolution Help?

Postby Izawwlgood » Thu Nov 03, 2011 2:05 pm UTC

Actually, females living past menopause is a trait that was positively selected for.
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