While we can agree that evolutionary life exhibits no progress,
perhaps it has a general direction?
In a quick survey of textbooks on evolution, I couldn't find a single
one with the word "trends" or "direction" in the index. In the heated
zeal to eradicate the notion of progress in evolution, many
neodarwinians have banned any notions of trends or direction in
evolution whatsoever. Steven Jay Gould, one of the most outspoken
naysayers about evolutionary trends, is actually one of the few
biologists who even discusses the idea.
The central metaphor in Wonderful Life, Gould's entertaining book about
the reinterpretation of the Burgess Shale fossils, is that the history
of life can be thought of as a video tape. One can imagine rewinding
life, and by some divine miracle, changing a pivotal scene at the
beginning, and then rerunning life again from that point. This
time-honored literary technique reached its apex in the all-American
classic Christmas movie It's a Wonderful Life, from which Gould adapted
his title. In this nearly archetypal drama, Jimmy Stewart's guardian
angel replays Stewart's life without him.
If we could replay the epic story of biological life unfolding on Earth,
would it progress in a similar story as the one we know? Would life
recapitulate any of its familiar stages, or would it stun us with
contrary alternatives? Gould spins a masterful narrative of why he
thinks we would not recognize life on Earth if evolution could be run
But since we have this magical tape of life mounted in our machine,
there are further, and perhaps more interesting, things to do with it.
If we turned out the lights, flipped the cassette at random, and then
played it, would a visitor from another universe be able to tell if the
tape was running properly forward or unconventionally backward?
What would the screen show if we played the epic Wonderful Life in
reverse? Let's dim the lights and see. The story opens with a glorious,
bluish Earth wrapped in a very thin film of living things, some mobile,
some rooted. The cast of character types totals in the millions, half
of them insects. In the opening scenes, not much happens. Plants morph
into endless shapes. Some larger, very agile mammal things dissolve into
similar, but smaller mammal things. Lots of insects melt into other
insects, while some wholly new insect creatures appear. They too
gradually merge into others. If we inspect any single character and
follow it in slow motion, it's difficult to discern much sensible change
going either forward or reverse. To speed the show, we fast-forward
(fast-backward to us).
The screen shows life becoming sparse on the planet. Many, but not all,
of the animal creatures begin to shrink in size. The total number of
kinds of things decreases. The plot slows down. Living creatures inhabit
fewer roles, and the roles change less and less as the tape proceeds.
Life steadily collapses in scope and size until it becomes small, bland,
and naked to the elements. In a very boring ending, the last variety of
animated things disappear as they melt into a single tiny amorphous
To review: a wide, complex, convoluted web of diverse forms just
collapsed into a relatively simple, unitary speck of protein that mostly
just copies itself.
What do you think, friend from Thor? Is the speck the alpha or the
Life surely has a direction of time, but beyond that, neodarwinists
would argue, nothing is sure. Since there are no directional trends in
organic evolution, nothing about life's future can be forecast.
Therefore the unpredictable nature of evolution is one of the few
predictions we can make about it. Neodarwinists count on evolution being
unpredictable. Who could have guessed while the fishes leaped in the
oceans -- the "pinnacle" of life and complexity at the time -- that the really
momentous long-range work was being done by some ugly freaks in dried up
mud pools near land? Land, what's that?
The postdarwinists on the other hand keep bringing up the word
"inevitable." In 1952, engineer Ross Ashby wrote in his influential book
Design for a Brain, "The development of life on earth must not be seen
as something remarkable. On the contrary, it was inevitable. It was
inevitable in the sense that if a system as large as the surface of the
earth, basically polystable, is kept gently simmering dynamically for
five thousand million years, then nothing short of a miracle could keep
the system away from those states in which the variables are aggregated
into intensely self-preserved forms,"
Real biologists cringe when "inevitable" is used in the same sentence as
evolution. I believe the reflex is a vestigial response from the time
when inevitable meant "God." But one of the few legitimate uses for
artificial evolution -- that even orthodox biologists will grant it -- is as a
test-bed for directional trends in evolution.
Might there be some fundamental constraints in the physical universe
that channels life along a certain grain? Gould addresses this concern
by comparing the possibility-space of life to the metaphor of "a very
broad, low and uniform slope." Water dropped randomly onto this slope
trickles down, eroding a chaotic path of microcanals. Newly hatched
channels are reinforced as more water flows down, quickly carving out
small valleys and permanently setting the location of succeeding larger
In Gould's metaphor, each tiny groove represents the historical timeline
of a species. The initial groove sets the course for succeeding forms of
genus, family and taxa. In the beginning, where the groove meanders is
totally random, but once established, the course of the following
canyons are fixed. Even though he admits his metaphor has an initial
slope that "does impart a preferred direction to the water dropping on
top," Gould insists that nothing disrupts the sure uncertain course of
evolution. In his favorite refrain, if you replay this experiment over
and over again, starting with a blank slope each time, you would get a
vastly different landscape of valleys and peaks each run.
The curious thing is that if you actually set up Gould's thought
experiment as a real test in a sand box, the results suggest an
alternative view. First thing you notice as you repeat the experiment
over and over again, as I have, is that the landscape formations are a
very limited subset of all possible forms. Many landforms we are
familiar with -- rolling hills, volcano cones, arches, hanging valleys -- will
never appear. Thus one can safely predict what general structure the
valleys and subsequent canyons will take: gentle gullies.
Second, while the starting groove begins at random in response to a
random falling drop, the shape of further channel erosion follows a very
homogeneous course. The canyon unfolds in an inevitable sequence.
Continuing Gould's analogy, the initial drop is the first species on the
scene; it might be any unexpected organism. Although its traits cannot
be predicted, the sandbox analogy says that its descendants unfold
somewhat predictably, according to trends inherent in the makeup of
sand. So while there are points in evolution where results are sensitive
to initial conditions (the birth of the Cambrian explosion could be one)
this by no means rules out the influences of large trends.
Evolutionary trends were once promoted by prestigious biologists at the
turn of the last century. One version is known as orthogenesis.
Orthogenic (straight) life advanced in a direct line, from organism A
through the alphabet of life to organism Z. A few orthogenesists in the
past really thought evolution proceeded without branching: imagine a
ladder climbing upwards, each species stationed on a rung, and every
rung closer to heavenly perfection.
But even those orthogenesists who weren't so linear were often
supernaturalists. They felt that evolution had direction because it was
directed. The directing forces were supernatural purpose or some
mysterious vital force that infused living things, or God himself. These
notions were clearly outside the ken of science, so what little
attraction the idea had to scientists was poisoned by its attraction to
the mystical and new-agey.
But in the last several decades, godless engineers have made machines
that set their own goals and seem to have their own purpose. One of the
first to discover self-direction within machines was Norbert Wiener, the
original cybernetic man. Wiener writes in 1950: "Not only can we build
purpose into machines, but in an overwhelming majority of cases a
machine designed to avoid certain pitfalls of breakdown will look for
purposes which it can fulfill." Wiener implied that at a certain
threshold of complexity of mechanical design, emergent purpose was
Our own minds are a society of mindless agents; purpose emerges from
that mix in exactly the same way purpose emerges from other
nonintentional vivisystems. In a very real sense, a lowly thermostat has
a purpose and a direction -- to find the set temperature and hold it there.
Astoundingly purposeful behavior can emerge from purposeless
subbehaviors cultivated in software. Rod Brooks's MIT mobots built with
bottom-up designs perform complicated tasks based on decisions and goals
which percolate up from simple goal-less circuits. Genghis the robot
insectoid wants to climb over phonebooks.
When evolutionists shook off God from evolution, they believed they had
shaken off any trace of purpose and direction. Evolution was a machine
without a designer, a watch made by a blind watchmaker.
Yet when we actually construct very complex machines, and when we dabble
with synthetic evolution, we find that both run by themselves and
acquire a sliver of their own agenda. Is the self-organizing
order-for-free that Stuart Kauffman sees in adaptive systems, and the
teleological goals that Rod Brooks can grow in machines, enough to
suggest that evolution -- however it came about -- might have also evolved
some goals and directions of its own?
If we look we may find that direction and goals can emerge in biological
evolution from a mob of directionless and goal-less parts, without
invoking vitalistic or supernatural explanations. Experiments in
computational evolution confirm this inherent teleogism, this
self-produced "trend." Two complexity theorists, Mark Bedau and Norman
Packard, have measured a number of evolutionary systems and concluded,
"Just as recent studies of chaos have shown that deterministic systems
could be unpredictible, we claim that deterministic systems may be
teleological." For those with an ear that burns at the combined sound of
"goal and evolution," it helps to consider this trait less as a
conscious goal, plan, or willful purpose, and more as an "urge" or
In the following list I suggest possible large-scale, self-generated
tendencies in evolution. Tendencies, as I'm using the word here, are
general and provide for exceptions. Not every lineage in a category will
follow that trend.
As an example, take Cope's Law, a principle often found in textbooks.
Cope was a swashbuckling bone collector in the 1920s who put dinosaurs on the map in more ways than one. He was a pioneer dinosaur surveyor and a tireless promoter of these exotic creatures. Cope noticed that, overall, mammals and dinosaurs seemed to increase in size over time. When studied carefully by later paleontologists, though, his observation applies to only about two-thirds of the cases on record; one can find plenty of exceptions to his rule even in the species lines he had in mind. If Cope's law was without exceptions then the largest living things on Earth would not be "primitive" fungi as large as city blocks hiding under the forest floors. Still, there is definitely a long-term trend in evolution that small things such as bacteria have preceded big ones such as whales.