Difficulty understanding evolution

[Adamchiv]

Here is the second installment of my friend's response.

"
Where complex structures like a nose and mouth are concerned, it must be appreciated that they did not arise as a single mutational event, but developed as stepwise elaborations of primordial structures. In multicellular invertebrates that are either sessile or that do not benefit from movement in a straight line (e.g. sea cucumber, slime mold) there is no selective advantage to development of a midline around which structures are placed symmetrically. However, in multicellular vertebrates for whom movement is a straight line is advantageous for targeting food sources, escaping predators, etc., development around a midline has a selective advantage. Symmetrical development around this midline helps maintain this selective advantage (fins on either side of the fish vertebral column, legs on either side of the early amphibians), and this arrangement thus dominates the anatomy of multicellular vertebrates. The nose is not a single structure but a complex one that connects both to the respiratory system and the brain. It is situated around the midline, with parts placed symmetrically on either side of the midline. The same holds for the mouth, which is just a part of the digestive system. While it’s theoretically possible to find a mouth at, say, the top of the forehead in the midline, evolution of the digestive system occurred in a coordinated fashion with the central nervous system. For the mouth to be at the very top of the head, the esophagus would then have to travel through the brain without disrupting brain function, which depends on communication between neurons on either side of the midline, and which was also evolving with the digestive system. Given the arrangement of these structures in primordial species, it is highly unlikely that any single genetic event could effect such a dramatic rearrangement. Moreover, were that to happen, it is prohibitively unlikely that the new arrangement would confer a selective advantage.

The notion that complex structures arise as stepwise changes in corresponding systems found in ancestral species also holds for networks like the circulatory system. Circulation arose to allow cells deep inside solid organs receive needed oxygen, and once the system developed, it is not feasible to imagine new organ systems arising that would obtain oxygen by some other method. Note that in insects, which are invertebrates whose evolutionary tree goes back to ancestral invertebrates that did not have a circulatory system, such a system does not exist, and cells receive oxygen through conduits that connect from the surface of the body. The insect system is not too different from that of the invertebrate sea cucumber. It’s not surprising that the insect system is not well adapted to vertebrate organisms with very large organs that may be billions of cells thick. So, the insect system is built on the tubule structure also found in the sea cucumber, while the arterial/venous system is descended from the oxygenation system of early vertebrates.

The underlying motive force for skepticism about complex structures evolving rather that being designed by an intelligence stems, in my view, from a lack of appreciation of the amount of time evolution has been taking place. Most people cannot really get a handle on a time frame of 40 million centuries, which is a reasonable estimate of the time since life first appeared. A lot of genetic experiments that failed can take place over that expanse of time. "

This is an amazing answer, simple enough for me to understand yet answers my biggest misunderstandings! Superb work

 

[gabi123]

Essentially, think of evolution as a bell curve. There is a certain path for every human, but a minority stray away. Mutations, as you described, happen not in terms of evolutionary theory. They could be from disease, or elsewhat.

 

[Adamchiv]

Essentially, think of evolution as a bell curve. There is a certain path for every human, but a minority stray away. Mutations, as you described, happen not in terms of evolutionary theory. They could be from disease, or elsewhat.

I thought mutations were genetic defects that can be passed down through generations? Surely there were a lot of mutations early on that effected small groups and tend to have little effect in large groups later on when the species gene pool is strong

 

[Pythagorean]

Mutations are something that happens - it's a neutral word. Whether they are a "defect" or an "adaptation" depends on how the mutation affects organism function and how you define functionality in the first place.

 

[BillTre]

In addition, new mutations can reverse the effect of other mutations, either directly or indirectly.
The genome can be considered a string of characters (of A, T, C, or G).
Changes can be made.
These can be transmitted to offspring and compose their genome.
The breeding population's genomes are the gene pool selection acts upon.
The character string can be mutated again and might (with a low probability) exactly change a mutation back to what it was before. This would be a back mutation.
In addition, a mutation at another place in the genome might make a change affecting some process that reverses the effect of the first mutation (through perhaps some physiological process) that will make the phenotype (what the organism looks like) like it was before the first mutation was acquired. This is sometimes called a suppressor. The original mutation would still be there, but its effect would be "muted".

 

[Adamchiv]

I didnt mean to put defect, I shouldve put change instead. I was just trying to recognise what causes mutations, I thought that it was mostly to do with changes in offspring rather than desease etc

 

[rootone]

There a number of possible reasons why a mutation can occur.
One is that the DNA replication chemistry, while it's wondrous and has 'error checking', it isn't 100% perfect.
Mistakes can happen in such a highly complex set of chemistry.
Mutation may also arise due to the interference of factors external to the replicating process itself.
Ionizing radiation even at background levels is a well known example,
https://bioethicsarchive.georgetown.edu/achre/final/intro_9_5.html

 

[BillTre]

Mutations can also come in a variety of changes:
1) change on a single base (A, T, C, G) to a different base
2) addition of one or more base to a particular location in a sequence (insertion)
3) deletion of one or more bases to a particular sequence (deletion)
4) take and section of sequence and flip it around (inversion)
2, 3, and 4 can result from either chemical treatments, x-rays, gamma-rays, experimental insertions, natural biological inserts (like transposons or viruses), or other stuff(??). These are known as breakpoint mutations because physical breaks have to be formed in the DNA for them to happen.
Juxtaposing different genetic elements can also have effects on gene expression by among other things bringing control elements closer to a coding sequence. Breakpoints can do this.

 

[Chris Miller]

We know evolution doesn't have a conscious mind...

How?
I like De Chardin's view of evolution as "the rise of consciousness."

 

[rootone]

How?

Because there is a perfectly good explanation of evolution (backed up with evidence) that does not require a conscious mind

 

[phinds]

How?
I like De Chardin's view of evolution as "the rise of consciousness."

Evolution may be looked at at the rise of consciousness, but that is NOT the same as saying that evolution has a conscious mind, a concept that is patently ridiculous unless you are talking about a god in which case you are on the wrong forum.

 

[rootone]

Evolution may be looked at at the rise of consciousness ...

Only if taking an anthropocentric point of view regarding humans beings as a goal of evolution.
99%+ of modern lifeforms on Earth have not developed self awareness, yet they continue to exist and evolve.

 

[Chris Miller]

Ray Kurzweil, in "The Age of Spiritual Machines" grants evolution a small IQ. I'm not talking about a god (unless one defines "god" as existence). I'm talking about a universe (existence) that would appear to have some objective beyond mere survival and some small ability (given time) to meet this objective.

 

[phinds]

Only if taking an anthropocentric point of view regarding humans beings as a goal of evolution.
99%+ of modern lifeforms on Earth have not developed self awareness, yet they continue to exist and evolve.

No argument. I did not suggest that it was a good idea to consider it that way, just that one COULD should one choose.

 

[phinds]

Ray Kurzweil, in "The Age of Spiritual Machines" grants evolution a small IQ. I'm not talking about a god (unless one defines "god" as existence). I'm talking about a universe (existence) that would appear to have some objective beyond mere survival and some small ability (given time) to meet this objective.

Positing a universe that has ANY objective IS positing a god, or at best metaphysics. In either case, it is not physics.

 

[Chris Miller]

Positing a universe that has ANY objective IS positing a god.

Are you not part of the universe?

 

[phinds]

Are you not part of the universe?

What does that have to do with anything ?

 

[Chris Miller]

We are tools of evolution. Look how fast computers and AI are evolving. Nothing has changed evolution-wise from the big bang, except the pace.

 

[Ryan_m_b]

We are not the tools of evolution and Ray Kurzweil will say anything, fix any graph and cherry pick any data to support his quasi-religious belief in the singularity. Evolution is a biological process of change in allele frequency in populations over time. Saying that evolution is a tool of the universe to create consciousness within the universe is nothing more than a semantic fallacy of implying the universe acts with intent.

This thread ran its course, there's no discussion of evolution ocuring anymore so thread locked.