Stasis: Life Goes On but Evolution Does Not Happen
It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, wherever and whenever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.
However, it hasn't turned out that way. Nature seems not to like such orderly schedules much. Evolutionary biologist Donald Prothero admits:
In four of the biggest climatic-vegetational events of the last 50 million years, the mammals and birds show no noticeable change in response to changing climates. No matter how many presentations I give where I show these data, no one (including myself) has a good explanation yet for such widespread stasis despite the obvious selective pressures of changing climate.
The first major discovery was that stasis was much more prevalent in the fossil record than had been previously supposed. Many paleontologists came forward and pointed out that the geological literature was one vast monument to stasis, with relatively few cases where anyone had observed gradual evolution.
Similarly, biologist and paleontologist Niles Eldredge, best known for his theory of punctuated equilibrium ("sudden appearance" of phyla, classes, and orders, followed by long periods of stasis) has noted:
As a PhD candidate, I set out to collect trilobite fossils from all over the Midwest. And I started to realize that the fossils I was collecting -- whatever point in time I was in -- all looked the same. I found no evidence of change. At first I put that down to my inexperience..."I'm not good enough to see the obvious changes that are here."
An evolutionary biologist at the University of Oslo, Kjetil Lysne Voje, offers an explanation for stasis:
The most wide-spread explanation is stabilising selection. It suggests that the advantage for a species which is already well adapted to its environment will be to avoid changing much. It is a type of natural selection that favours the average individuals in a population because changes are disadvantageous. Changes are a drawback and stabilising selection will discard deviations from the well-functioning norm.Unfortunately, Voje has, in his last sentence, blown up his own thesis.
"Stabilising selection is a very good explanation for stasis, as it helps a species remain unchanged. But it has some problems, as it is hard to conceive of an optimal form that would not change in the course of millions of years," says Voje.
Species often explode suddenly into life, as in the Cambrian explosion, which even Darwin found to be a problem for natural selection. (See the new short video from Discovery Institute, The Information Enigma.) Some of them do not persist beyond the age to which they are adapted. That does not require an explanation.
But others just settle down to long eons where they don't change much, no matter what the environment. And "stabilizing selection" does not account for that. The cockroach, for example, is still around and still easily identifiable after perhaps 350 million years. The 350-million-year-old coelacanth fish and the 300-million-year-old horsetail grass survive largely unchanged.
When the coelacanth, supposed extinct for 70 million years, turned up in the Indian Ocean in 1938, it disappointed biologists who hoped for a living proof of Darwinism.1 It is a living proof of non-Darwinism.
Similarly, a recently discovered 425-million-year-old crustacean showed no significant changes in internal body parts, compared to present-day specimens. One researcher called it "a demonstration of unbelievable stability." But the stability is only unbelievable if we start with Darwin's assumption that "natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest." Apparently not.
Similarly, comb jellies, far more complex than sponges, evolved before sponges, more than 550 million years ago. As one scientist put it, "It's just wild to imagine" that comb jellies evolved before sponges. Why? What are the assumptions here? Stasis followed by eventual extinction may well prove to be even more common in the history of life than we have so far seen.
Prominent textbook author Douglas J. Futuyma wrote recently:
One of the most important shifts in evolutionary biology in the past 50 years is an increased recognition of sluggish evolution and failures to adapt, which seem paradoxical in view of abundant genetic variation and many instances of rapid local adaptation.
Vast Time, Little Change
We now have "increased recognition," but we do not yet have any theory that accounts for it. Here are some examples of life forms that show little if any change over vast periods:
37 million years ago: Asymmetrical whale skulls found. They were formerly thought to be a much more recent adaptation for echolocation.
45 million years ago: "Living fossil" primates (tarsiers), which can communicate by ultrasound, are largely unchanged today. Similarly, a species of mites has parasitized an ant species ever since then. "Much longer than thought." Blood-feeding insects date from this period as well (the Eocene).
49 million years ago: A spider in amber, surprisingly, turned out to be clearly a member of living genus Eusparassus.
100 million years ago: Crickets have shown no significant changes since that period. The oldest mammalian hair found so far also dates back to this time. Said one researcher, "Perhaps mammalian hair does its job so well that it does not need to evolve."
120 million years ago: A fossil pregnant lizard shows that live birth among land reptiles is very old, not recent. "It implies physiological adaptations, like adequate blood supply to the embryos and very thin shells -- or no shells at all -- to allow oxygen supply, evolved very early on." Meanwhile, a lacewing insect fossil, found at the 120 million year stratum in China, prompted the comment that, "Seems that at this rate of evolution, we'd need trillions of years, maybe lots more, to see any substantial change," because of its similarity to current lacewings.
126 million years ago:Plant mimicking stick insect found. Described as "one of the grand-cousins" of today's mimics.
150 million years ago: Bird-like dinosaur Archaeopteryx's feather structure is identical to that of living birds. Also, a crab fossil from this era looks just like a modern crab. "It's amazing, but if we did not know this was a 150-million-year-old fossil, we might think that it came from today's ocean."
160 million years ago: A Jurassic placental mammal "redefines mammal history," showing mammals are much older than formerly thought.
165 million years ago: Giant female (leg span 15 cm) golden spider found in China "extends the fossil record of the family by approximately 35 Ma and of the genus Nephila by approximately 130 Ma, making it the longest ranging spider genus known."
167 million years ago: Snake fossils found. The characteristic snake skull and its parts appeared long before snakes lost their legs. "This new study makes it clear that the sudden appearance of snakes some 100 million years ago reflects a gap in the fossil record, not an explosive radiation of early snakes."
190 million years ago: A nest site for dinosaur eggs suggests that dinosaurs kept an eye on their young. The findings "suggest that Massospondylus returned to the site repeatedly, laying their eggs in groups in the earliest-known case of 'colonial nesting.'" (Middle Jurassic reptiles may have cared for young as well.)
200 million years ago: "Living fossil" eel survives from this period.
243 million years ago: Recent pollen studies suggest that flowering plants originated in this period (Middle Triassic) rather than 140 million years ago (Early Cretaceous), as previously thought. "'With a few differences...the pollen from the Middle Triassic look exactly the same as the angiosperm pollen from the Early Cretaceous,' explained Prof Hochuli."
270 million years ago: Tracks show that amphibians have been "using the same swimming technique" all this time.
280 million years ago: Apparent almost-live birth in sea reptiles (mesosaurs). "The study of these exceptionally well-preserved fossils suggests that mesosaurs were either viviparous (pushing back this mode of reproduction by 60 million years) or that they laid eggs in advanced stages of development."
300 million years ago: Harvestmen spiders (European daddy long legs) were much the same as today. "It is absolutely remarkable how little harvestmen have changed in appearance since before the dinosaurs."
360 million years ago: The lamprey is little changed after all this time.
400 million years ago: The oldest fossil insect found so far (a springtail) dates from this period. So does wood. The findings "suggest that wood evolved at least 10 million years earlier than previously documented."
450 million years ago: Horseshoe crabs are largely unchanged from then to today. Oddly, this remarkable stability is referred to as "strange evolution." That's rather like describing Michelangelo's David as engaging in "strange motion." Neural circuitry for complex social behavior also dates from this period, at least.
473 to 471 million years ago: Liverworts, the earliest known land plants, date back this far.
505 million years ago: Marine acorn worms appear. "Discovery pushes fossil record back 200 million years"
515 million years ago: The eyes of sea-dwelling predators are highly sophisticated, "rivaling the most acute compound eyes in modern arthropods." Cambrian animals also had modern hearts, "a sophisticated system complete with heart and blood vessels."
520 million years ago: Tulip-shaped entoproct is spotted, once thought to date back only to the age of the dinosaurs (150 mya).
525 million years ago: Pterobranches, a small colonial marine invertebrate, show little change from this period. The find "demonstrates stasis in pterobranch morphology, mode of coenecium construction, and probable feeding mechanism over 525 million years."
540 million years ago: Killer shrimp, nearly a meter long, lived
550 million years ago: Comb jellies thrive, challenging the assumption that sponges were the most ancient animals: "They are much more complex than sponges -- they have nerves, muscles, tissue layers and light sensors, all of which the sponges lack."
555 million years ago: Worm tracks found.
550-560 million years ago: Oldest organism with a skeleton found, shaped like a thimble, with foot-long spines.
600 million years ago: Jellyfish that uses a light display lived at this time.
635-715 million years ago: Fossil tintinnid (paramecium-like one-celled organisms with flask-shaped shells) found.
760 million years ago: Otavia,
800 million years ago: Organisms formed shells (biomineralization). This is very early in the known history of life.
1.1-2.3 billion years ago: Complex (eukaryote) cells existed then. The study authors note, "Accurate estimation of the divergence time of the extant eukaryotes is a fundamentally important but extremely difficult problem owing primarily to gross violations of the molecular clock at long evolutionary distances and the lack of appropriate calibration points close to the date of interest."
2.3 billion years ago: Sulfur bacteria from this period look the same as bacteria today.
2.48 billion years ago: Oxygen-breathing bacteria that survive today lived on land, "100 million years earlier than previously thought."
3.3 billion years ago Beach-living microbes have been dated from this time.
The File Grows Unwieldy
Many more instances could be provided, but the file grows unwieldy already. Some of these finds, particularly the older ones, might need revision, but the recorded examples of stasis will almost certainly grow. Many life forms (and processes) just hang around indefinitely, while others come and go. Yet, even despite catastrophe, all life never died out.
We see a pattern of increasing complexity in the history of life, but that pattern requires some qualification: There were complex creatures in the Cambrian (see Anomalocaris, above). Although there is a great variety of complex life forms today, there is a great variety of simpler ones too. They are much more numerous. Humans, by far the most complex life form, are very late arrivals -- but we are unique. So it is not clear that there is a natural law favoring the growth of complexity.
How do evolutionary biologists address the picture? In the face of so many unexpected examples of stasis, defensive habits of thought and speech linger. Some examples:
Absurd levels of evidence for stasis are demanded:"We'll doubt evolution when we find fossil rabbits in the pre-Cambrian!" The challenge isn't whether to doubt evolution but how to interpret the pattern in a reasonable way. We should not expect rabbits, to be sure, unless we also expect the vegetation they live on. But what about this? A Boston College research team found fossils of freshwater multicellular animals from the pre-Cambrian, and reported:
These assemblages contain multicellular structures, complex-walled cysts, asymmetric organic structures, and dorsiventral, compressed organic thalli, some approaching one millimetre in diameter. They offer direct evidence of eukaryotes living in freshwater aquatic and subaerially exposed habitats during the Proterozoic era. The apparent dominance of eukaryotes in non-marine settings by 1Gyr ago [one billion years ago] indicates that eukaryotic evolution on land may have commenced far earlier than previously thought.
Which is nearly twice as long ago as the Cambrian explosion.
Grasp at minor, reversible changes."See! Evolution at work! Finch beaks changed slightly in a dry period!" The trouble is, a 2011 study was the first to combine data from short periods such as 10-100 years with the fossil record over millions of years, and determined that "rapid changes in local populations often don't continue, stand the test of time or spread through a species." A change, the researchers reckoned, must persist for a million years to become permanent. If they are correct, most popular "evolution at work" stories do not pass this test. They are often best interpreted as ecology-driven variations back and forth on a given theme, like beak shape.
Finds that -- taken together -- suggest a pattern are treated as if they are unique.The classic phrase "earlier than thought" is used repeatedly to describe unrelated early fossil discoveries that suggest stasis. No wonder readers are seldom encouraged to see a pattern: Each "earlier than thought" shortens the time available for a Darwinian account of evolution from Earth's cooling to the present.
Choice of words often obscures basic facts. Consider, for example, Darwin's term "living fossil," which is admitted by New Scientist to be "oxymoronic." They are right. All fossil members of the species are dead, of course; the living members are not fossils, and most will die without ever becoming fossils. "Durable species" might be a more appropriate term.
Then there are the everyday terms that cloud thinking: "Primitive," for instance, as in the "primitive woolly rhino fossil." That rhino species adapted to an ice age and became a dominant life form of its type. How primitive is that? "Missing link" assumes that a long, slow, orderly procession of missing links, like Mayor Bloomberg's Ida fossil, must exist. Why must they, when there is so much evidence of short periods of rapid change followed by long periods of stasis? Consider also the role of "surprising." Why is it "surprising" if a beetle is unchanged for 20 million years? If evolution is rare, occurring in short bursts, and stasis is the norm, then many existing life forms will turn out to be "older than thought." The approved terminology serves mainly to impede our grasp of the larger, largely non-Darwinian, pattern.
If the history of life is not what Darwin and his followers have supposed it to be, we should next look at what the big picture, taken together, can tell us.
(1) Michael Denton, Evolution: A Theory in Crisis (Bethesda: Adler & Adler, 1986), pp. 157, 179, 180. The fish is a rhipidistian, a group from which the ancestor of amphibians such as frogs and toads was thought to have come. So surely it must feature "transitional" anatomy. It doesn't. It is all fish and no frog.
See the rest of the series to date at "Talk to the Fossils: Let's See What They Say Back."