Thursday, 20 October 2011

Evolution (20 OCT 2011)

When Donna posted about "Evolution", she started her analysis in the garden but finally had to take a walk to the Niagara Falls to find the true meaning of the word.

So I have two problems with this challenge : (1) the scope of this blog is confined to my back garden (2) I live in a suburb of London where you would struggle even to find relics of the past century. In fact, I would go so far as to say that the back garden of my house, built in the early 1930s, is as historical as it gets around here ...

At first, there were snails .... primitive limpet-like snails date back to about 600 million years ago.

baby snail on a poppy leaf

It's believed that slugs evolved from snails. The evidence is that the saddle of a slug contains the remnants (or the initiation?) of a snail shell.

one of the more attractive slugs in my garden

Being a "scientist", my beliefs are based on data that I have studied. I have observed snails and slugs co-existing in my garden; one day I'll peer at a snail stuck to the under-side of a hellebore leaf, the next day I'll uncover a slug soaking up the moisture retained under a stone. To me, one creature doesn't seem advanced or superior compared to the other, they are just doing their own thing (which mostly involves nibbling at my favourite plants).

Mosses evolved about 350 million years ago, whereas grasses are relatively new on the scene becoming widespread about 55 million years ago, 10 million years after dinosaurs became extinct. Well, that's what paleontologists thought until they found grass in dinosaur droppings.

moss is a gymnosperm (non-flowering plant)
grass is a monocot while clover is a dicot
Flowering plants, angiosperms, are split into two major groups monocots (with one seed leaf) and dicots (with two seed leaves). It's not clear why these two groups evolved separately, but they both thrive in my lawn. Equally confusing is the development of pollination, mosses evolved before flowering plants and grasses evolved after, yet they both rely on wind pollination, whereas the petals of the dicots in my flower beds indicate that they are hoping for insect pollination.


It is hypothesised that the evolution of grasses led to an increase in grazing animals, which opened up the landscape in preparation for human existence.

apposable thumb

The humans' ability to manipulate tools to extract bone marrow (brain food) from carcasses resulted in increased intelligence and more ingenious ways of using tools, setting up a feedback loop. This theory made sense until bones, pre-dating humans, which seem to have been crushed by stone tools were discovered.

Even so, humans have used their intelligence to change nature for better and for worse. 

hybrid tea rose grews amongst wild rose bushes

What this human has concluded in this landscape is that :
(1) we are lucky to be living in a forgiving era where species adapted for different conditions can live side-by-side
(2) small changes on a continuous basis make the biggest difference in the long run. You only need to watch a plant growing to understand this.

I'm linking this post to Donna's meme Word for Wednesday : EVOLUTION / EVOLVE
Please check out the other posts at :

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20 comments: said...

Very, very interesting approach and analysis. So what do you conclude about snails and slugs and the adaptive change? That their evolution was without consequence? That in 600 million years they did not evolve much? If I remember fossils of snails, they are very large, although I am not sure on this. This is really a good subject to look into. Your observation seems to be in order and not in dispute because they do seem a little like one in the same, making a living in the same manner almost. But if it is an evolutionary adaptation so the slug does not need a 'house', to me he got the short end of the stick by needing moisture all the time. This one is a puzzler with lots of questions. Makes you respect them more since they have been around so long too. And your notes on grasses and mosses are very interesting too. This is a post that generates a lot of thought. Good word!

b-a-g said...

Thanks Donna - I read that slugs lost the shell because even though it retains moisture, it doesn't offer much protection from predators and gets in the way when the snail tries to hide. I'm not sure what I believe at the moment, I'm quite exhausted after studying a billion years of evolution in one evening. I'll read all the other Evolution posts tonight.

Esther Montgomery said...

If I were a slug, I'd long for a shell.

I'm puzzled by what you say about mosses. If they don't have flowers, how do they have pollen? And what are the little structures on stalks which grow up from moss - which I'd taken, until now, to be flowers?

The Sage Butterfly said...

You took this challenge and ran with it. I like the facts about plants of which I was not interesting!

One said...

I'm happy to hear that you are exhausted after studying a billion years of evolution in one evening. I think you caused many of us to be exhausted doing research and scratching our heads.

Nevertheless I enjoy reading all the different takes on Evolution.

I only see snails and never slugs in my garden. Why?

Why do puppies have flat nose but gets sharper and longer as they grow older?

HolleyGarden said...

I realize that we really don't know very much. The scientists state one thing, then later on, find out something else. I agree, however, with your statement that small changes on a continuous basis make a big difference in the long run. It makes me wonder what little changes are at work now.

b-a-g said...

Esther - the moss "flowers" that you've seen are actually capsules containing spores. There's a link in the post in blue and this link has more details :

Thanks Sage Butterfly - I should have stated that I am not an expert on evolution, I've just read some articles on the internet to prepare for this post. My approach was more like a school-child writing a biology essay.

b-a-g said...

Thanks a lot One ! - As I am not a global expert on slug lifestyles - I can only guess that Malaysia is too hot and dry for slugs, at least snails have some hope of retaining moisture. I'm afraid to say that I know even less about puppies. I couldn't leave a comment on your post, I really enjoyed your interpretation of Evolution, your pet dog has become a celebrity.

Thanks Holly - I wonder how human beings will continue to evolve now that we are no longer hunter-gatherers. Maybe we'll develop better close-range eyesight for working on computers or bigger backsides for sedentary occupations.

Carolyn @ Carolyn's Shade Gardens said...

What struck me is that "facts" that scientists were so sure of later turned out to be wrong. Evolution is such a tricky thing based on guess work and everything we may think is true now could be out the window in a decade.

catharine Howard said...

A little science elegantly and lightly dropped in. I enjoyed this.

Donna said...

Fascinating post. I love to learn new facts. Moss is one of my favorite plants. It grows freely given the right conditions. To think it has been around millions of years is amazing.

Cat said...

Interesting about the snails and slugs...I agree, I would long for the 'house' too. In response to One, here in hot and dry Texas, we have both snails and slugs. I can see slug trails along the stone path in the morning light.

Andrea said...

As I go back and read all the posts, the more I believe that Donna is so amused by what she caused us to do. I thought I had a difficult time contemplating on the post, till I see yours, imagine reading a lot to do these post! But you really made a very intellectual piece, which all of us enjoyed. By the way, when I recently saw the root structures of cycas for a previous post i also searched for it, found it was here since the dinosaurs. And I concluded it's because of their types of roots.

b-a-g said...

Carolyn - I suppose that studying any kind of history is like fitting a jigsaw puzzle together. The picture evolves when new pieces are added.

Thanks Catherine, Donna & Cat - Most of the people I know are non-scientists. I like to encourage people to think about science, without forcing it on them.

Thanks Andrea - Yes, Donna has a lot to answer for! ... and I have discovered a new fascination in "evolution". When I was researching for this post I found some interesting stuff that may appear in future posts.
I checked out cycas, living fossils, they look intriguing.

Jennifer@threedogsinagarden said...

Many thought provoking ideas in this evolution post. When I sat down to think about how I might handle the word, I tried to think about what things in the garden might have ancient origins. I thought of dragonflies, but not snails. As I continued to read through your post, I found that I learned more than a few things. Great job! I enjoyed my visit.

Alistair said...

Slugs and snails, which came first. If this was thrown at me I would quickly say and be convinced that slugs came first and then developed a shell for protection. On the other hand the Neanderthals who apparently were physically stronger arrived before the humans. Personally I think I have the brain of a Neanderthal and the body of a human.

Janet/Plantaliscious said...

I like your second conclusion, sort of "little and often", I can work with that!

Carolyn ♥ said...

Fascinating! Donna has certainly caused some "deep thinking" in the blogosphere. My life is so busy busy lately that I'm afraid I will have to be content to enjoy the fruits of your study and analysis... invigorating!

Autumn Belle said...

Now, I shall look at the snail, slugs, frogs, turle and the occassional visitor like snakes and lizards in a different light. I need to respect them for being in existence since time immemorial ;>)

b-a-g said...

Alistair - I wonder if Neanderthals had a passion for gardening ...

Thanks Jennifer, Janet, Carolyn, Autumn Belle - researching for this post made me realise that there is no such thing as the truth, just what we know so far.

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