Creation (2 page)

The Origin of Life

Begotten, Not Created

L
ife is made of cells. For that reason, the vast array of these microscopic, gloopy bags is beyond description. In one single species, us for example, there isn't an absolute number, but of the fifty trillion or so cells that an adult might have, there are hundreds of types: from astrocytes in the brain to the zymogenic cells of the stomach. Along with that variety comes an assortment of dimensions. The longest cells are neurons in the spine, which stretch all the way to your big toe. If size is important, then you should turn to sex. Among the largest cells in humans are the eggs, just about big enough to see with the naked eye. And the smallest cells are their counterparts, sperm. However, what men lack in size they make up for in numbers: the average adult male can produce ten billion sperm per month, whereas women carry a finite number of eggs, one released every month from alternating ovaries between puberty and menopause. Women are born with all of their eggs already in place—the one that made you was made while your mother was growing inside her mother's womb, meaning that your first cell began its life inside your grandmother. Other than eggs, almost all cells are invisible to the naked eye, and even with a microscope most look unremarkable: tiny, colorless blobs bound by a fractionally less colorless membrane, generally sitting in a fairly nondescript, dimly lit swill. In labs, when we freeze tissue and slice it into slivers less than one-hundredth of a millimeter thick on glass slides, the cells appear packed together in dense abstract patterns. Or we grow them in broth, where they can be seen free-floating like blurry stars in an off-white sky. We stain cells in hues of pink and purple, and more recently in fluorescent greens and reds, to help visualize their inner workings. But in a live body, most are opaque as jellyfish.

Each type of cell is a highly specialized member of a community, working in unison with others to build a fully functional organism. Every process of our lives is a result of those cells performing their jobs. As you read this sentence, the muscle cells around your eyeball contract and relax to control the movement of your eyes from left to right. If you glance above this page now and look at something in the distance, a ring of muscle cells achieves focus by stretching the clear cells in the lens. You move your eyes effortlessly, but this action requires intricate unconscious coordination. Photons of light pass through your lens and hit the cone and rod photoreceptor cells at the back of your eye, in your retina. There they are harvested and converted into electrical impulses that zoom through neurons, via the optic nerve, up to the brain for processing, perception, and, with luck, understanding. Each movement: every heartbeat, thought, and emotion you've ever had; every feeling of love or hatred, boredom, excitement, pain, frustration, or joy; every time you've been drunk and then hungover; every bruise, sneeze, itch, or snotty nose; every single thing you've ever heard, seen, smelled, or tasted is your cells communicating with one another and the rest of the universe.

Douglas Adams once suggested that Earth was not the most appropriate name for our planet, as most of the surface is not solid dirt and rock, but water. Yet if you really wanted to name our home world after a feature that truly differentiates it from the other eight hundred or so planets that we have found, it would be Cells. Earth, uniquely as far as we know, is bursting with life, and every living thing on our planet is made of cells. Bearing in mind that nine out of ten things that have ever lived on Earth are already extinct, the number of cells that have ever existed is utterly incalculable.

This is a very modern understanding. Biology is a young science, at most 350 years old, and only 150 in terms of a fuller, mature view with comprehensive and universal rules. Physics has an older pedigree. By the mid-seventeenth century, scientists had mapped areas of the cosmos with future-proof accuracy. Isaac Newton was drawing up a set of rules that explained why things move the way they do, and why we can stand on Earth and not float away. But what are now known as the life sciences were a long way behind. The reason for this is that the starting point for most scientific advances is to look at things and work out why they are the way they are. Unlike the stars and planets, no one had even seen—or at least identified—a cell before 1673.

At that time, science itself was forming. Gentlemen scientists such as Newton and Robert Hooke had formed the world's first scientific body, the Royal Society. But the man who first peered into the minuscule world of the cell at the birth of cell biology was not one of the esteemed, bewigged gentlemen of science. The unlikely beginning of the story of biology must be credited to a Dutch linen merchant named Antonie van Leeuwenhoek.

The business of making and selling cloth was inextricably linked to the development of better optical lenses, as merchants checked the density of fibers and therefore the quality of their fabric using magnifying glasses like a watchmaker's loupe. Van Leeuwenhoek was a skilled and meticulous lens grinder, working in Delft, the capital of Dutch drapery. He specialized in a technique that involved pulling apart a hot glass rod and squashing the ends back to form a ball, but was secretive about this process, as it had made him the greatest microscopist of his day. Van Leeuwenhoek's lenses were tiny fat drops not much bigger than a peppercorn, and he attached them to handheld contraptions nothing like current microscopes. His were rectangular copper plates, about one inch by two inches, with a hole at one end to hold the rotund glass-bead lens. On one side there was a silver spike to hold the specimen in front of the lens, held by a screw that could be turned for focusing. It was the fatness of Van Leeuwenhoek's lenses that gave them their superior magnification.

At least, that was his technological advantage. His other key attribute was insatiable curiosity. Van Leeuwenhoek simply liked looking at small things through his lenses. While I hope the paper cut described in the introduction is entirely imagined, Van Leeuwenhoek deliberately invoked exactly the same repair process out of unbridled curiosity. In a letter published in the Royal Society's official journal
Philosophical Transactions
in April 1673, Van Leeuwenhoek wrote, “I have divers times endeavored to see and to know, what parts Blood consists of; and at length I have observ'd taking some blood out of my own hand, that it consists of small round
globuls
[sic].” We think that he was looking at red blood cells, and this appears to be the very first recorded sighting of individual cells.
¹

As his microscopy skills improved he began to look at all manner of bodily samples and fluids. He went on to scrape the matter from between his teeth and observed the bacteria that cause plaque. At the tail end of the seventeenth century, Van Leeuwenhoek was becoming something of a celebrity for his exploration of a microscopic kingdom hidden in plain view. King William III of England and other dignitaries visited him to see what he had seen. One discovery, however, was kept private: his own semen, although he attested in his notes that the sample was acquired “not by sinfully defiling myself, but as a natural by-product of conjugal coitus.” In this act, which it is perhaps best not to dwell on, he saw sperm for what they are: single cells. He also discovered cells in a bead of water from a local lake and saw what we now loosely call protists: single-celled creatures that include algae and self-powered swimmers.

Van Leeuwenhoek was the first person to definitively see individual red blood cells, sperm, bacteria, and free-living single-celled organisms. This last group he gave a cute name, animalcules, and in the 1670s he sent drawings of his discovery to the Royal Society in London. The fellows expressed skepticism, not least because when they asked Robert Hooke, their resident microscope expert, if he could see the same creatures in water from the Thames, he initially saw nothing.

Hooke's expertise in looking at tiny things was unparalleled, having published a stunning and popular volume a decade earlier,
Micrographia: or Some Physiological Descriptions of Minute Bodies made by Magnifying Glasses
. Rarely has a book been so accurately subtitled. It contains, as you might expect, annotated drawings of very small things. His microscope was a simple six-inch tube with two lenses, and a baseball-size crystal sphere to magnify the illuminating flame. Many of the images generated by this kit are now very familiar, including a giant foldout of a flea, and a terrifying close-up of the eyes of a hover fly, which looks staggeringly similar to contemporary photos taken with an almost unrecognizable descendent of Hooke's tools: the electron microscope. Samuel Pepys picked up a copy of
Micrographia
and noted in his diary that it was “the most ingenious book that ever I read in my life.”

Quite right. But there's a significant irony contained within this magnificent tome. One of Hooke's detailed illustrations is of a longitudinal cross section of some bark from a cork tree. There in the meticulous picture are conjoined units making up the overall structure. In the text, Hooke uses the term
cell
to describe these units. In reality they are the dead walls that once housed cork tree cells. He chose the word as it derived from the Latin
cella
, meaning “cubicle,” but noted that they were air filled, which helped explain cork's buoyancy. Hooke had seen the remnants of cells, named them cells, but did not for a moment imagine that his observations were of universal living units, nor the permanent legacy of the name.

That is how cells were discovered. But where did they come from and how were they formed? With curiosity and technology, Van Leeuwenhoek had pulled back the curtain to reveal an undiscovered kingdom, but progress was fundamentally hindered by a resolutely unenlightened ideology.

The Origin of Cells

The origin of the cells Van Leeuwenhoek glimpsed remained elusive. Obviously, people knew that sexual intercourse between a male and a female often resulted in a new life, but, perhaps because most sex goes unobserved, an entirely fanciful view of the origin of cells remained vexatiously persistent.

Spontaneous generation was the most popular origin-of-life story for thousands of years. The first substantive explanation of spontaneous generation comes from Aristotle, the unsung father of biology. In his book
Animalia
(
The History of Animals
), written in the mid–third century
BCE
, he describes the genesis of certain species:

So with animals, some spring from parent animals according to their kind, whilst others grow spontaneously and not from kindred stock; and of these instances of spontaneous generation some come from putrefying earth or vegetable matter, as is the case with a number of insects, while others are spontaneously generated in the inside of animals out of the secretions of their several organs.

Animalia
is a fascinating book, probably the first great biology textbook. It's crammed with observations and conclusions about a huge range of species, some of which are dodgy.
²

In spontaneous generation, Aristotle described an idea that persisted until the nineteenth century, during which time dozens of examples materialized. The Roman writer Vitruvius casually referred to spontaneous generation when advising architects in the first century
BCE
:

[L]ibraries should be toward the east, for their purposes require the morning light: in libraries the books are in this aspect preserved from decay; those that are toward the south and west are injured by the worm and by the damp, which the moist winds generate and nourish, and spreading the damp, make the books moldy.

In the sixteenth century Ziegler of Strasbourg claimed that lemming hordes originated from storm clouds.
³
Indeed, following Van Leeuwenhoek's discoveries, all manner of speculation on the origin of cells and life was put forward, all involving spontaneous generation. In seventeenth-century Brussels, Jean Baptiste van Helmont—marked in history as a respected scientist, the father of the chemistry of gasses—described an experiment in which he sealed a sweaty shirt in a vessel with some wheat and let it ferment in his dank castle basement for twenty-one days. Lo and behold, this concoction gave rise to mice.
⁴

It's all too easy to mock the ignorance of the past, and we should be wary of it. Though spontaneous generation was a persistent idea, it is not a solid scientific concept. All the misplaced examples, most notably when describing the genesis of larger beasts, were born of incomplete or poor observations. There are few more elementary questions than that of the origin of life, either in terms of the origin of new life from existing life or the more fundamental absolute origin of life, ex nihilo.

It was almost two hundred years after Van Leeuwenhoek first saw cells before the concept of spontaneous generation was thrown out. The final dismissal bears all the hallmarks of good science: rigorous observation and a testable, predictive hypothesis. But it also comes with the stamp of pure drama: an international cast and a generous helping of money, fame, and betrayal.

The Birth of Cell Theory

The quality of microscopes improved steadily throughout the eighteenth and nineteenth centuries, and the popularity of the study of small things grew accordingly. The biggest advances came not from exploring the microscopic animal kingdom, but from looking at plants and algae. That different parts of plants were composed of cells was apparent in the first few decades of the nineteenth century, though the ubiquity of cells in all living things was not. Much of this work was carried out in Germany, and the textbooks carried names describing a range of observed structures: Körnchen, Kügelchen, and Klümpchen (granules, vesicles, and blobs). But while the description of tissues was progressing, the root of its genesis was not. It was not until 1832 that the birth of cells was first described. A Belgian baron named Barthélemy Dumortier watched cells in an algae grow longer and longer until a partition wall appeared and one cell became two. Other scientists soon replicated the work and observed it in different algae and plants.