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Question
Hi, I am researching the history of evolutionary theory, and what else we know now.I was hoping you could answer some questions that I have.

What were some of the early theories of evolution?

What did these theories mean(what was the story behind them)?

How have these theories grown into today's discoveries?

Could you please get to me by next week Tuesday, or as soon as possible.
Thank you,
Maddy

Answer
Hi Maddy.

Historically, there had been observations even by the ancient Greeks, Romans and Chinese that there were somehow areas in the anatomies of various plants and animals that seemed to them to indicate a connection.  However, understand that they knew nothing of genes, how things were inherited, what a mutation was, even what the heart did, or what the brain even was.  They had no idea we had a circulation system using a pump.  Nothing.  However, they did notice that all animals with a skeleton had a head, body four limbs and a tail....

(and yes, humans have tails.  Google "Humans with tails" and see some photographs.  Very likely if a child then was born with one, they saw it as an omen of some god.)  

So very likely, with this observation, we might correctly assume that the ancient Greeks came up with the beginnings of, maybe not evolution, but a connection among vertebrates.  There were no early theories at this time.... only a noticing of connection.  

As for what this connection meant, they had no clue.

The most brilliant idea was Darwin's.  And even he didn't see too much in the 1830's as he was a passenger.... the naturalist....aboard the Beagle.  He simply collect specimens, dried them, and brought them back to England.  He had a bird collection, that he gave to the leading British ornithologist of the time...all finches.

You might have a look at this site:

http://en.wikipedia.org/wiki/History_of_evolutionary_thought

And as well, Google "HOX genes".



But all of the things he saw, and all of the items he brought back seemed to him, early on, that these were just a jumble of items.  It wasn't for several years that he began to make connections.... that some of the finches had thicker bills on different islands, yet were the same bird, leading him into the beginnings of how animals adapt to their environment....and in so adapting, changed thru mutations.  (This idea of mutations wasn't fully understood, nor even accepted until long after his death.)   On islands with only very thick seeds, those had a preponderance of thick billed finches.  And on islands with thin seeds or narrow ones, the shape of the bill differed.  (And since that time, observers have noticed on all islands, if the rain fall is slight, only the most hardy of plants with the thickest seeds survive.  Offspring with slight bills  born to parents died after fledgling, since their bills were too weak to split the seed.  However, in times of lots of rain, all survived, so the mutation for thin bills on various finches did survive, and that gene stays alive and well even today.  It is just that not always every year, will those survive.

Darwin's idea of "we are all related" took him easily 15 years to come up with a workable hypothesis, and because other biologists were honing in on how all living things are related, he was being pushed to publish his idea, which he did in 1859...."Origin of the Species".  Had he not done so, the development of this idea would have been credited to a different person.

(Interestingly there was this idea that Lamarck had.... that acquired mutations could be passed on.  However with not too much thought, this can be eliminated.... One can cut off dogs' tails, and them breed them together.  But all the puppies will still have long tails.And cut off those puppy's tails, again, only long tailed puppies will be born.    Only if there is a mutation in the genetic makeup of the animal, will ever short or stubby tailed dogs be born.

How have these theories grown into today thoughts?

The true end to creationism, or intelligent design ended in the 1950's with the discovery of how DNA works.  DNA had been known about since the late 1800, but it was Crick and Watson who proved how it "unzipped" and then "rezipped"..... the double helix.  This discovery earned them a Nobel Prize, and ended any doubt whatsoever, that we are all related on this planet... that we all are made of DNA, and the more alike it is in its sequencing, the closer we are evolutionarily.  After that, creationism and intelligent design took their seats in the area of religion, not science.

(As an example, all bilateral animals share HOX genes...scorpions, birds, spiders, grasshoppers, apes, humans, horses, etc.  But those that are not bilateral...octupi, clams, hydra, do not have these genes, thus one could begin to assume that we are more closely related to insects than we are to octupi or squid.

Ping around on Google for other sites.  Evolution of Man is always a good one.

Evolution of the horse too is hugely interesting....from a little guy (eohippis) not much bigger than a 60 lb dog, to horses that weigh today 2000 lbs.

All in all we live in an exciting time for science.  2000 years ago, everything was caused by gods.  Today?  This quote by Neil deGrasse Tyson is really spot on.....

"Does it mean, if you donít understand something, and the community of physicists donít understand it, that means God did it? Is that how you want to play this game? Because if it is, thereís a list of things in the past that the physicists at the time didn't understand [and now we do understand.] If thatís how you want to invoke your evidence for God, then GOD IS AN EVER RECEDING POCKET OF SCIENTIFIC IGNORANCE thatís getting smaller and smaller and smaller as time moves on - so just be ready for that to happen, if thatís how you want to come at the problem."
~Neil deGrasse Tyson

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I've been a public school teacher for 26 years. My major was history, but along the way, picked up minors in math, biology, zoology, and other life sciences. My whole life has been on one side of the desk or the other. Husband and Dad were both MDs so science and medicine was a natural for me. My dad once told me that I knew more medicine than most doctors. I can easily answer almost any life science question, most history questions, and lots of medical questions.

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