Pebbly beach in The Blind Watchmaker book

[Blind Watchmaker]

Hi all,

I know that this question is not directly about evolution but I can't find a better place for it.

I would really like to see an example (a photo) of the pebbly beach that Richard Dawkins is talking about in "The Blind Watchmaker" book. In chapter 3 ("Accumulating Small Changes") Richard Dawkins gives an example of a pebbly beach:

"If you walk up and down a pebbly beach, you will notice that the pebbles are not arranged at random. The smaller pebbles typically tend to be found in segregated zones running along the length of the beach, the larger ones in different zones or stripes. The pebbles have been sorted, arranged, selected. A tribe living near the shore might wonder at this evidence of sorting or arrangement in the world, and might develop a myth to account for it, perhaps attributing it to a Great Spirit in the sky with a tidy mind and a sense of order. We might give a superior smile at such a superstitious notion, and explain that the arranging was really done by the blind forces of physics, in this case the action of waves. The waves have no purposes and no intentions, no tidy mind, no mind at all. They just energetically throw the pebbles around, and big pebbles and small pebbles respond differently to this treatment so they end up at different levels of the beach. A small amount of order has come out of disorder, and no mind planned it. The waves and the pebbles together constitute a simple example of a system that automatically generates non-randomness. The world is full of such systems".

I'm not sure that I understand what he is talking about, my intuition is telling me that on such a shore we should see first a heavy big pebbles that the waves couldn't push much, and farther (away from the sea shore) we should see a stripe of a smaller pebbles, that the waves throw stronger away, but when I searched in Google Images the only example that I could find that "Fits" Richard Dawkins's example, is this:

https://previews.123rf.com/images/amoklv/amoklv1510/amoklv151000040/46400336-pebbly-beach-of-ibiza-balearic-islands-spain.jpg

 

But as you can see, it's just the opposite of what I imagined... first there are small pebbles, and only then there are large pebbles.

Is that what Richard Dawkins talked about in his example? If so, how the waves can explain that?

Can you help me find a better photo that illustrate what he means?

I would really like to see how it looks.

Thanks!

 

[MigL]

Maybe, for that particular beach, and those particular rocks, you have your wave action wrong.

Maybe the waves are strong enough, coming in, to push those size rocks onto shore, but after losing strength on the rocks/sand, are not strong enough to pull the larger ones back out.

The point of the quote is not whether the rocks are sorted large to small, or small to large, but that they are sorted in a particular order.
IOW the process generates order.

[Strange]

When I think of pebbly beaches, I think of larger pebbles furthest from the water with smaller pebble and gravel/sand where the water is. Or a line of large pebbles with smaller ones either side. Never really thought much about the mechanism. But it must vary from one beach to another.

On Chesil Beach, they are sorted along the length of the beach: https://en.wikipedia.org/wiki/Chesil_Beach (sort of)

[Blind Watchmaker]

7 hours ago, Strange said:

When I think of pebbly beaches, I think of larger pebbles furthest from the water with smaller pebble and gravel/sand where the water is. Or a line of large pebbles with smaller ones either side. Never really thought much about the mechanism. But it must vary from one beach to another.

On Chesil Beach, they are sorted along the length of the beach: https://en.wikipedia.org/wiki/Chesil_Beach (sort of)

I looked at the link that you gave and the pictures there, I couldn't see any order in the pebbles on this beach.

 

10 hours ago, MigL said:

The point of the quote is not whether the rocks are sorted large to small, or small to large, but that they are sorted in a particular order.

"Sorted in a particular order"

Isn't it large to small, or small to large? what other order can you think of?

And your theory about how the waves do that may be right, but I would like to see a photo of such a beach that represents what Richard Dawkins thought about when he gave that example in his book.

 

Edited December 23, 2019 by Blind Watchmaker

[Janus]

10 hours ago, MigL said:

Maybe, for that particular beach, and those particular rocks, you have your wave action wrong.

Maybe the waves are strong enough, coming in, to push those size rocks onto shore, but after losing strength on the rocks/sand, are not strong enough to pull the larger ones back out.

The point of the quote is not whether the rocks are sorted large to small, or small to large, but that they are sorted in a particular order.
IOW the process generates order.

Wave action, even on the same stretch of beach can have varying effects.  For example, not too far from here is a beach with a large basalt rock formation on the tide line.  At high tide it is completely surrounded by water and during low you can walk up to its base.

Now the point is that on its landward side during low tide, there is a rock debris field that on some days is exposed and on others can be completely buried under sand.   You never really know what you'll find any time you visit.   The same is true for a small cove near a place we stay at  further South.  On one day you go down to it and it is pretty much just sand, and then the next it will have bands of pebbles and rocks.  You can have two bands of with a band of just sand between.

There is sorting going on, but just not in a steady large to small fashion. The interaction between the  next incoming wave and the water going back out from the previous one is not a simple one.

[Strange]

19 hours ago, Blind Watchmaker said:

I looked at the link that you gave and the pictures there, I couldn't see any order in the pebbles on this beach.

I wouldn't expect you to be able to discern individual pebbles; it is a big beach! You would probably have to go there. 

 

Quote

The pebbles are well-graded, coarsest near Chesil (Chesilton) and diminishing in size towards Bridport, and it is said that fisherman landing on the bank at night can judge their position by the size of the pebbles.

http://www.southampton.ac.uk/~imw/chespeb.htm

[Blind Watchmaker]

9 hours ago, Strange said:

The pebbles are well-graded, coarsest near Chesil (Chesilton) and diminishing in size towards Bridport, and it is said that fisherman landing on the bank at night can judge their position by the size of the pebbles.

http://www.southampton.ac.uk/~imw/chespeb.htm

Thanks, but I don't think that that's what Richard Dawkins was talking about in his book. It seems that your quote is talking about different shores, large pebbles on one shore (near Chesil) and smaller pebbles on another shore (towards Bridport). I think that Richard Dawkins was talking about different zones or stripes of pebbles with different size on the same shore.

 

[uncool]

3 hours ago, Blind Watchmaker said:

Thanks, but I don't think that that's what Richard Dawkins was talking about in his book. It seems that your quote is talking about different shores, large pebbles on one shore (near Chesil) and smaller pebbles on another shore (towards Bridport). I think that Richard Dawkins was talking about different zones or stripes of pebbles with different size on the same shore.

 

The quote doesn't read that way to me at all; if they were separate shores, why would a fisherman need to look at pebbles to determine which shore he was on?

Also, look at a map - Chesil Beach and Bridport are part of one continuous coastline.

[Strange]

8 hours ago, Blind Watchmaker said:

Thanks, but I don't think that that's what Richard Dawkins was talking about in his book. It seems that your quote is talking about different shores, large pebbles on one shore (near Chesil) and smaller pebbles on another shore (towards Bridport). I think that Richard Dawkins was talking about different zones or stripes of pebbles with different size on the same shore.

It is the same (very long) beach.

It may not be what Dawkins was talking about - it sounds as if he is just talking about the heterogeneous distributions in strips or zones along the beach. But it is another example of how the environment can create an impression of order.

I'm not quite sure what the question is here. It is pretty obvious by visiting any beach that the pebbles are not uniformly mixed. So are you looking for more detail on the mechanisms that cause pebbles to get separated by size? Or what?

On 12/23/2019 at 3:54 AM, Blind Watchmaker said:

Is that what Richard Dawkins talked about in his example? If so, how the waves can explain that?

A quick search found these, I have only skimmed them so don't know how relevant they are:

https://royalsocietypublishing.org/doi/full/10.1098/rspa.2011.0562

https://www.researchgate.net/publication/223721922_Concepts_in_gravel_beach_dynamics

https://www.researchgate.net/publication/311093229_Grain-size_distributions_on_high_energy_sandy_beaches_and_their_relation_to_wave_dissipation (so it applies to sand as well as pebbles)

It looks like the different height and slope of the beach (also created, partly, by wave action) plays a role in the distribution of sizes.

[Blind Watchmaker]

8 hours ago, uncool said:

The quote doesn't read that way to me at all; if they were separate shores, why would a fisherman need to look at pebbles to determine which shore he was on?

Also, look at a map - Chesil Beach and Bridport are part of one continuous coastline.

If the fisherman see large pebbles then he knows that it's the shore near Chesil, if he see small pebbles then he knows that it's the shore near Bridport.

Is it really so hard to understand?

 

3 hours ago, Strange said:

It is the same (very long) beach.

It may not be what Dawkins was talking about...

I'll check it later, thanks.

 

[Strange]

1 hour ago, Blind Watchmaker said:

If the fisherman see large pebbles then he knows that it's the shore near Chesil, if he see small pebbles then he knows that it's the shore near Bridport.

And if the pebbles are medium sized, they know they are somewhere in between

[uncool]

3 hours ago, Blind Watchmaker said:

If the fisherman see large pebbles then he knows that it's the shore near Chesil, if he see small pebbles then he knows that it's the shore near Bridport.

Is it really so hard to understand?

 

It's not, and that doesn't answer the question I'm asking.

The point is that a fisherman might use this method because of the lack of easier methods. If there are two completely separate shores, determining the shore is as easy as finding which side of a divide you are on. It's only hard because of the continuity between them.

[Ken Fabian]

I'm not sure pebbles on a beach would be the best example of nature separating things by size or density - often they do appear well mixed although I have observed differentiation. Dawkins may have seen something like this -