What did Charles Darwin consider "almost the most wonderful fact I ever heard of?"

I was reading 'Origins' - by Lewis Dartnell. It's a book that shows how Earth's history shaped our human history. It is as extraordinary a study of human civilization I've ever read (and one single chapter - Chapter 7 - is worth the price of the book alone) but that isn't what this post is about...

Lewis Dartnell starts Chapter 5 with the question: Who built the pyramids?

Well. Everyone knows who built the pyramids.

If you wanted to be matter-of-fact about it, Egyptians built the pyramids, helped by 20,000 - 30,000 masons, skilled laborers, builders, surveyors, engineers, slaves, under orders of their god-king, over 4500 years ago. The oldest and largest of these - the Great Pyramid of Giza, built during the time of the pharaoh Khufu, also called Cheops, still stands now.

But to go beyond the obvious...

Turns out the Great Pyramid is primarily made of out limestone (as well as granite, but more of limestone than granite) blocks. As an aside, on the limestone blocks ... each block weighs 2.5 tonnes, which according to the Weight of Stuff would translate to the weight of 20 - 25 baby elephants. No one knows how chubby baby elephants are in any given year, let's just assume they are plump, which is a cheerful prospect, so go with 20. So, a block of limestone is as heavy as 20 chubby baby elephants. There are around 2.5 million blocks of limestone and granite in the Great Pyramid and these were lifted hundreds of feet, without fork lifts or cranes or heavy equipment. Yes, building the pyramids was an astonishing feat indeed. But that was a minor digression. If you look closely, Lewis Dartnell writes, you'll see the limestone blocks used in the pyramids are made out of a great many tiny coin-like disks.

This round, convex-shaped, coin-like disk is the fossil of an extinct species.

Their name? Foraminifera.

What were the creatures called the foraminifera?

Apart from being quite a mouthful to pronounce (if you wanted to be real friendly, you could call them 'forams', which is what folks who work with them call them, apparently).

Foraminifera are single-celled creatures that lived in the oceans millions of years ago.

How do tiny single-celled creatures have coin-like disks two-inches to six-inches wide?

Apparently, these single-celled foraminifera built giant shells around themselves.

These shells are intricate and extraordinary and made of calcium carbonate.

Limestone, if you recall, is made of calcium carbonate.

See the connection here?

The foraminifera created the calcium-carbonate shells that formed limestone deposits, that were quarried by the Egyptians, then carried hundreds of miles away to be cut and shaped, and stacked for 200+ layers, one on top of the other, to create the Great Pyramid of Giza.

These limestone deposits were abundant across North Africa and Europe. Our friends, the 'forams' lived in these waters and when they died, their calcium carbonate shells drifted to the bottom of the oceans and joined to form great big blocks of limestone.

Two famous figures noticed this -

The ancient Greek historian, Herodotus, in 5th century BCE said that foraminifera made up the limestone rocks that were used to create the Great Pyramid of Giza. Hundreds of years later, Charles Darwin (1809 - 1882) noticed it as well. What Darwin said in a letter to his friend W.B. Carpenter about a tiny creature's engineering ability was.... (see Sarah Kaplan and Ben Guarino in a Washington Post article now archived):

“... almost the most wonderful fact I ever heard of. One cannot believe that they have mental power enough to do so, and how any structure or kind of viscidity can lead to this result passes all understanding.”

Given Darwin noticed enough phenomena to change the course of the science of evolution, this was worth following up on... or so it seemed to me. So I looked up the articles.

This is what Sarah Kaplan (and her co-author) have to say about the foraminifera -

Not only do some forams build their own shells, many are fierce hunters, capable of snatching multicellular prey from the water column using their pseudopodia. Still others harbor algae companions, which live inside their shells and provide energy through photosynthesis. This symbiosis has allowed some forams to become positively huge; the ancient Egyptians used one extra-large group, called Nummulites, as coins. Meanwhile, humans can only marvel at the powerful organic cement they use to hold their shells together; some scientists are studying this substance in hopes of improving our own building materials.

In Kaplan's article, you will find images of foraminifer's many different shapes.

Check out #4.

Here is the precise definition of when nummulites formed according to Britannica -

Nummulite, any of the thousands of extinct species of relatively large, lens-shaped foraminifers (single-celled marine organisms) that were abundant during the Paleogene and Neogene periods (65.5 million to 2.6 million years ago). Nummulites were particularly prominent during the Eocene Epoch (55.8 million to 33.9 million years ago), and limestone of this age that occurs in the Sahara is called nummulite limestone in reference to the great abundance of its contained fossil nummulites.

This was what astonished Darwin... the fact that unicellular creatures, with no brain and no nervous system could build such intricate, extraordinarily big structures around themselves... using specific materials and algae, which then turned into calcium carbonate fossils, which were then became blocks of limestone, which was mined and used to create the pyramids.

Who says, small creatures cannot build great things?