Just a few miles down the road there is "home improvement" store. It's a large, low building flanked on one side by a place for plants and garden supplies and on the other end by a chain-linked bit of asphalt that used to hold lawn tractors and gas grills. I say "used to," because the store is empty.
It was built in 1995 as a Builder's Square. When it opened, the little Ace Hardware down the street and a local garden center next door went out of business. Only two years after it opened, the blue and gold markings of Builder's Square were replaced by the green "HQ" of Home Quarters Warehouse. It stayed that way for a couple of years more. Then an even larger store opened a few blocks away, this time with the orange blaze of Home Depot. Within months, the green HQ store was closed. Now the orange store has been flanked by an even bigger, newer store, bearing the blue markings of Lowe's. The orange store is starting to look a little shabby. Ace to Builder's Square to HQ to Home Depot, and maybe now to Lowe's. Surely there's someone with another logo -- purple or yellow or maybe chartreuse -- lurking on the horizon.
This commercial theater of dancing colors, played out on a few blocks of one street near St. Louis, is just an expression of a much larger drama. What happened in this competition and succession of businesses was guided at least as much by events that happened at corporate headquarters hundreds of miles away, and by other struggles that took place in other cities, as it was by competition along that street. But this kind of succession, in which apparently successful establishments are swept aside by new entries, is a common feature of the business world.
One of the forces at work is something called late mover advantage. Big players in an area of business can seem unassailable. They already hold the "niche." In fact, their name may be so associated with a certain line that it's hard to think of that industry without thinking of them. But Goliaths fall to scrappy upstarts every day. With every passing year, stores and fixtures that were once new become more out of date and needing of repair. Locations that were once prime, find themselves moored far away from new development and the new stores that draw in shoppers. Inventory accumulates. While the ever spreading web of stores means more opportunity, it also magnifies the cost of each mistake. All the while the late movers watch from the wings, noting each error, searching for weakness, looking to copy what works, discard what doesn't, and insert themselves into the market at the time of maximum advantage.
Even those businesses that have been around for decades can suddenly find themselves in a struggle for their lives against competitors that didn't exist until recently. Ask Woolworths. Ask Sears. Ask GM.
Ask snails.
In the natural world, this sort of pattern is common. The niche for a certain mixture of activities can be held for a long time by a single species, or by a handful of closely related species. This dominance can last millions of years and spread over huge areas. But visit that same environment in the same location only a few million years later, and you may find a quite different creature filling the same role.
When Charles Darwin published On the Original of Species in 1859, the fossil record was like a dark room with a few scattered spots of dim light. Fossils had only been gathered from a few regions, there had been little systematic collection, and much of what had been found wasn't clearly identified. Against that murky situation, it wasn't surprising that Darwin's critics, like anatomist Richard Owen, were able to assert that the fossil record didn't show the type of gradual transitions Darwin had predicted. Even when the rocks were kind enough to present a specimen that was clearly an intermediate between two other forms, that specimen itself seemed isolated.
Critics pounced on Darwin's theory through this lack of evidence for gradual transition in the fossil record. A great deal of this was simply a form of reductio ad absurdum. Presented with a form that was at the mid-point between two species, the critics would scream about the absence of a specimen 3/4ths one and 1/4th the other. If something turned up that satisfied that complaint, they'd move to arguing over 7/8ths. No matter how fine a sequence is presented, there is always some gap that the determined reductionist can use as a wedge for their complaint. It worked in 1860, and it's still a mainstay of anti-science creationists.
Darwin, along with most of his supporters over the last century and a half, assumed that with sufficient exploration many of the gaps in the fossil record would be filled and his predicted pattern of gradual transformation would be confirmed. That was certainly true in many respects, as more and more fossils confirmed exactly the sort of large-scale transitions that had been predicted in Origin. But on a smaller scale, the gaps stubbornly refused to close. At many points in the fossil record, the transitions from one species to the next remained oddly abrupt, without evidence of transitional forms.
It was such a serious problem that even scientists who believed in evolution began to doubt Darwin's ideas about the way in which operated. Various forms of Lamarkism, involving the development of new species through the inheritance of acquired features, competed with natural selection during Darwin's lifetime, and they continued to attract followers in the decades that followed. When Darwin died in 1882, this alternate view of evolution experienced a kind of resurgence. Increasingly, natural selection seemed to be caught in a trap. The theory seemed inadequate to the task of explaining how the variations in species arose, or how traits were passed along, or how multiple species developed from a single source.
Darwin himself was deeply aware of the deficiency of his ideas in explaining the how of change and turned to an idea called pangenesis as a means of explanation. In this theory, each cell in the body produced a kind of local blueprint that was shipped down to the reproductive hot zone for exchange during sex. The presence or absence of these little capsules could affect the offspring. There was no real evidence behind the theory. Worse, what evidence there was increasingly argued against it. Pangenesis opened a host of new questions, provided few satisfactory answers, and its predictions about inherited features just didn't seem to match real world results. This gaping hole in the side of natural selection was another cause for the reduced acceptance of Darwin's ideas in the years immediately following his death.
However, the experimental evidence that Darwin needed to bolster his work had already been collected, and published, decades earlier. In the period from 1856 to 1863 (neatly framing Origin's publication at the end of 1959), Gregor Mendel cultivated nearly 30,000 pea plants. Growing that number of plants isn't unusual (modern farmers plant as many as 125,000 soybean plants in a single acre to maximize yield), but where most people plant fields of uniform seed, Mendel was carefully cross-breeding different varieties and noting the resulting offspring. Close observation of traits over generations of plants allowed Mendel to determine the way in which inheritance worked through dominant and recessive 'alleles' long before the genes themselves could be detected. He published his paradigm-altering observations in 1866 and sat back to… deafening silence. The paper, published in an obscure Moravian journal, languished for decades. Sadly, Darwin never became aware of Mendel's discoveries and Mendel never experienced the acclaim his work would eventually earn.
It wasn't until the start of the 20th century (a few years after Mendel's death) that Mendel's work was rediscovered and his experimental results replicated. Not only did the work revolutionize biology almost overnight, but it also provided the key to understanding how organisms had the flexibility to change while retaining traits through inheritance — both of which were required by Darwin's theory of natural selection. Over the next three decades a growing understanding of genetics and population dynamics would lend ever increasing support to Darwin's work. More evidence would come from every field of biology and paleontology, as strand after strand of supporting theory came together. The fossil record might not demonstrate gradual change, but year by year, paper by paper, the study of biology was gradually transformed from multiple, disconnected areas into a cohesive unified discipline — with Darwin's work right at the center.
The major complaints of Darwin's critics had been solved, but there was still that vexing problem of the gaps in the fossil record, the gaps that still refused to go away no matter how many specimens were collected. In 1942, evolutionary biologist Ernst Mayr made a large contribution to solving the problem. According to Mayr the gaps didn't exist because organisms changed abruptly. They changed gradually, just as Darwin (and by then, genetics) predicted. It was just that not all examples of a species were taking the same trip. Local populations — particularly small, isolated populations — could diverge from other examples of a species. A was still A in the living room, while another group of A was slowly becoming B behind the barrier of the bedroom door. For watchers in the living room, the apparently abrupt transition occurred when B, which had been gradually evolving off-stage, returned to replace its relatives. In this way, you could get a new species while the old species was still around. Or develop multiple species from a single stock.
By the early 1940s, the modern evolutionary synthesis was in place. It can be summed up in five simple statements:
- All evolution is consistent with genetic mechanisms.
- Evolution takes place gradually, through small changes.
- Natural selection is the overwhelming force driving evolution.
- Genetic diversity within a species is the raw material against which selection works to drive evolution.
- The rate of change is not constant, and different mechanisms are behind periods of rapid change.
The explanation of abrupt changes in the fossil record was given a more thorough examination in 1972 when paleontologists Niles Eldredge and Stephen Jay Gould published their paper on "punctuated equilibria." Like Mayr, they acknowledge the role of isolated populations in driving evolution. Under punctuated equilibria, if you were to peel back the layers of a particular bed of fossil bearing rock so that you were observing the presence of one species over time, you would not find a series in which A gradually adds more characteristics of B until the original species has been replaced. Instead you find A. Then A. Then A again… right up until the point where you find B (with, perhaps, A still living in the same area). It was this pattern — a long period of species stability followed by relatively abrupt change — that Gould detected in his studies of land snails and Eldredge saw in his fossils of trilobites.
Punctuated equilibria has often been touted by critics as proof that Darwin was "wrong," or that there's some great controversy within the scientific community about the mechanism of evolution. Neither is true. Punctuated equilibria doesn't overturn Darwin's theory in any sense — though it does confound some of what Darwin expected to find in the stones. Some critics have even tried to assert that punctuated equilibria provides some proof for a kind of "ongoing creation" in which new creatures are dropped into the mix from time to time. That's even further from the mark.
The critical word in punctuated equilibria is "relatively," as in relatively abrupt change. A change that looks sudden in the fossil record can still be quite gradual on most scales. Say, as an example, that human beings were to trip along for the next million years with a height around two meters tall, but then future exo-paleontologists find human beings averaging three meters tall only a million years later. That's quite a significant and sudden change on a geologic scale, but a million years is time enough for 50,000 generations of humans to come and go. In that million years, each generation would need grow an average of only two one hundreds of a millimeter to accomplish this "aburpt" change.
Punctuated equilibrium doesn't discredit Darwin's idea of gradual change. It doesn't require "hopeful monsters" (one of my favorite phrases in all of paleontology) to drive the progress. By any rational measure, the change from one generation to the next is quite small. What punctuated equilibrium did was simply to acknowledge that the general state of change was miniscule, that most organisms stayed the same for long periods. When scientists observe the sudden appearance of a species in a fossil record, what they're usually seeing is something akin to the causes behind that succession of hardware stores in my neighborhood -- events taking place out of town. The new species evolved gradually in some isolated location, then moved in on its cousins.
That's not to say that the gradual, wholesale change of a widely established species can't occur. There are a few very good examples of exactly this kind of evolution (known as phyletic gradualism) preserved in the fossil record. One of the best is found among the fossil manatees along the Pacific Coast of North America.
Sirens (the group that includes manatees and dugongs) arrived along America's West Coast during a tropical period in which the waters off the coast from California north to Canada supported warm, grass-filled bays more like those the Gulf Coast than anything seen in the area today. In that environment, manatees prospered, and several species sometimes shared the same area (Also sharing the fields of sea grass was a peculiar relative of the sirens, Desmostylus. When the first bones of this animal -- skulls and vertebrae -- were found, paleontologists confidently expected then to be matched up to a creature bearing flippers. But when a complete skeleton was finally uncovered, Desmostylus proved to have four legs. And four very foot-like feet. For twenty million years, Desmostylus paddled off America's west coast. Dietary evidence and the location of fossils suggests that it was entirely, or almost entirely, marine. But it had feet, and never evolved into a form with flippers.)
There were several types of manatee along the Pacific Coast, but around seven million years after they had arrived along with the period of tropical climate, the tropical climate departed. Water temperatures cooled. A period of mountain-building drove the land up and turned gradually-sloping shorelines into sharp cliffs. Areas that had been manatee-friendly bays filled with sea grass, turned into deep, cold water trenches. Most of the Pacific manatee species died out, but one of the smallest, Dusisiren, managed to hang on. Gradually, through a series of slow transitions that would have greatly pleased Darwin, Dusisiren increased in size and became better adapted for eating the new kelp beds that were then replacing the grass. Probably as a response to the insulation needed in colder water, the descendants of Dusisiren, now called Hydrodamalis grew much larger than the manatees and dugongs found in tropical and subtropical environments. As it got bigger, it gradually lost the tusks and specialized teeth other manatees use to uproot and eat grass. Its forelimbs changed from the standard manatee flipper into tough little "arms" capable of holding the heavy creature steady against pounding waves, or even "walking" over submerged ledges in search of kelp. All these changes seem to have happened very slowly, and also quite uniformly. By the early Pliocene, around 5 million years ago, big toothless Hydrodamalis had completely replaced his smaller forbearers — and was still growing.
When European explorer's unexpectedly encountered the creatures among a series of small islands off the coast of Russia, the last of the Pacific sirens reached lengths of more than eight meters (around 26 feet) and weighed in around 10 tons — a size that made them as long as the largest killer whales, and about three times as heavy. They formed a floating colony around the Arctic shore, and watched the explorer's with no apparent alarm.
If you're unfamiliar with the idea that there are such creatures in the Pacific, there's a very good reason. Less than thirty years after the animals, named Stellar's Sea Cows after their discoverer, were first encountered in 1741, the last one was killed and eaten by traders on their way from Russia to Alaska.
Manatees survived over twenty-five million years in the Pacific, but they didn't survive human contact.
Stellar's Sea Cow, as drawn by Georg Steller |
Back in the world of business, phyletic gradualism can seem as rare as it does in the fossil record. It can be difficult for an established corporation to fight off the pressure of a "freshly evolved" upstart. But it does happen. First movers have their own set of advantages. That's particularly true in technological fields where limited resources (often limited
human resources) and a specialized knowledge base can give the first entrant into a new area a virtual 'lock' on the field while competitors struggle to break in.
In more general commerce, early entrants don't enjoy that same edge, but they do have a foundation of pure experience that can sometimes turn the tide. A few miles in the opposite direction of my hardware parade is a small town where Wal-Mart moved in and existing local stores began to fail. But rather than folding its tent, Sears decided to make a different kind of play. They opened up a "Super Sears" on the scale of the Wal-Mart, but with a different mix of goods. Whether this punctuation of Sears' long equlibria will be effective is hard to say, but it's interesting to watch.
Wal-Mart itself is undergoing a kind of phyletic gradualism, growing from merely Brobdingnagian to more Galacticusian. Maybe that change will serve to keep the giant ahead of the circling Davids, but I wouldn't make a bet on it. Over the long term, evolution is particularly unkind to giants. It took twenty-seven years from discovery before someone ate the last Stellar's Sea Cow. I wouldn't make a bet on Wal-mart surviving that much longer.