The Arms Race…
Biological arms races are feedback loops caused by organisms evolving in response to
each other.
I. Human arms races. Technological advances made by one side in a conflict spur
advances in the other side and vice versa, leading to a feedback loop with rapid advances
on both sides. Similar patterns occur in nature.
II. Biological arms races. Feedback loops between predators and prey, parasites and hosts,
competitors for resources, competitors for mates.
A. Symmetrical Arms Races, or Competitive Arms Races. Characterized by
competition for resources, esp. intraspecific. Examples: plants competing for light,
males competing for females
B. Asymmetrical Arms Races, or Antagonistic. Characterized by attack-defense
dynamics, esp. between species. Examples: predators versus prey, herbivores
versus plants, parasites/diseases vs. hosts.
C. Significance of arms races. Adaptation to other organisms, rather than the
environment, as the major driver of evolution?
The race: Individual predators and prey animals race against each other in a very real
sense: the predator is running to catch its dinner, the prey runs to avoid becoming dinner.
Both are literally racing for their lives. But there is also an evolutionary race between the
predator species and the prey species.
The evolutionary race: Some prey are faster than others. The slowest ones tend to get
eaten by predators. Kill by kill, the gene pool changes. As a result the prey species
becomes faster, and harder to catch. Because the prey is evolving to become faster, the
predator must evolve as well. Slower predators miss too many kills. They starve, or are
unable to compete for mates and territories with their faster, better-fed kin. Gene pool
changes and the predator evolves
This explains why ancient communities are so different from modern ones:
Carboniferous predators and prey were slow-moving, slow-witted, slow-growing. Selection
by predators on prey, and prey on predators, lead both to become faster. This dynamic has
been called an ‘arms race’ .
HUMAN ARMS RACES…
Arms Race: The term arms race refers to competition between two powers in the
development of weapons. Human arms races have gone on for thousands of years (e.g.
longbows versus knights at Hastings). But the concept became widespread due to the
extraordinary pace of advances in the 20th century, particularly WWII and the Cold War
Example: flight aircraft in the 20th century.
Inter-war Years: dramatic advances in fighter technology. The ability to rapidly pursue-
or run from- enemy aircraft was usually the deciding factor in combat
Faster aircraft were designed in the interwar years. The Spitfire had a powerful engine
(Rolls Royce Merlin), better streamlining (closed canopy, retractible landing gear), and
more efficient, smaller wings (designed by NACA, forerunner of NASA). But once you built a
faster plane, the other guy would counter - making a plane as fast or faster, and your
advantage was lost.
WW2: in an effort to keep up with and surpass the enemy, faster aircraft were designed.
The enemy, however, is not sitting still – far from it.
The other side counters: 1944 saw the introduction of the first jet aircraft by Germany-
far faster and more powerful than propeller-driven aircraft. A first-generation jet fighter.
Probably the best fighter of WWII— but too little, too late to tip the balance of the air
campaign. After WWII, the UK and US develop their own first-generation jets (Meteor and
Shooting Star, respectively)
The Cold War: fearing a showdown, NATO and Soviets keep upping the ante. Every time
one side improved, the other did as well.
Eventually, this comes to an end: record of 3200 km/hr set in the 1980s. Modern
fighter aircraft are actually slower than the aircraft they were designed to replace. Why did
, the race slow and then reverse?
(a) running up against the laws of physics (high drag at supersonic speeds)
(b) Spending on the contest conflicts with other needs (roads, doctors, universities)
(c) Other factors may become more important in the contest (F-22 is slower but stealthy)
This is a symmetrical arms race:
Basic idea:
• Each side competes for the same goal (e.g., control of the skies)
• They up their game, you up yours- move by one side leads to an identical move by the
other
• Leads to dramatic improvements in performance
• Eventually the arms race has to slow down or stop, because:
(a) Further improvement becomes difficult, or
(b) Increased spending on the contest conflicts with other demands, or
(c) other factors decide the contest
(other examples would include the the nuclear arms race in the late 20 th century, battleship
arms race in the early 20th century)
Studying human contests is useful because we know the history of these events, so we can
understand the processes that drive the patterns. Evidence from the modern world and the
fossil record suggests that strikingly similar dynamics occur in nature.
SYMMETRICAL ARMS RACES IN NATURE…
Organisms in nature fight over resources such as light, water, food, and mates. This leads
to arms-race dynamics
Evolution of forests as an arms race: Forests seem still and peaceful, but are actually
the result of an arms race. Why are trees tall? The most effective shape for a solar collector
should be a wide structure low to the ground - solar cells work perfectly well at ground
level, after all
Light competition: Trees fight for light. If you’re at the top of the forest, you get light. If
you’re below the canopy, you’re in the shadows. You want to grow up above everybody
else so you get the light, and they are stuck in the shadows. Modern forests are the result
of an arms race that has played out over hundreds of millions of years.
Arms race in plants: Fossil spores show that the first plants on land were liverworts and
hornworts, almost half a billion years ago. These are creeping plants. They spread out over
the ground to collect light- an efficient way to distribute light-collecting tissues. They fight
for light by creeping over the top of each other
The stem: a new technology advances the race. Mosses invent the stem: a vertical
column that supports photosynthetic tissue above everyone else. Now you’re above the
other guy, and he’s in the shadow. But once everybody has stems, what do you do? You
need to get even higher- but you start having trouble getting water and nutrients to the top
of the plant
Vascular tissue: higher and higher… Vascular plants have vessels: hollow tubes that act
as pipes to carry water and nutrients up to the top of the plant. Now plants can get tall
Early forests: competition for light gets fierce:- Huge amounts of material are
invested in building stems to compete for light in the Carboniferous (billions of tons of the
stuff is buried- this is the origin of Carboniferous coal deposits that fuel the Industrial
Revolution). These plants grow by stacking new material on top of old material- an
inefficient way to grow
Growth by stacking: Primitive plants stack up material to make a stem, creating a
cylindrical trunk. Early on, the stem is short and very fat – stronger than it needs to be
(wasteful). Later on, tall and skinny (dangerously weak). The stem is never really well-
designed at any point in the trees’ life
Annular growth: A sheath of living tissue- cambium- goes around the entire stem, under
the bark. Annually deposits new wood around the stem (tree rings). The tree can grow up
and out. Efficient use of material: thin trunk for young, short tree, fat trunk for old, tall tree.
Stronger shapes: tree is fattest at the base where the loads are highest.
Biological arms races are feedback loops caused by organisms evolving in response to
each other.
I. Human arms races. Technological advances made by one side in a conflict spur
advances in the other side and vice versa, leading to a feedback loop with rapid advances
on both sides. Similar patterns occur in nature.
II. Biological arms races. Feedback loops between predators and prey, parasites and hosts,
competitors for resources, competitors for mates.
A. Symmetrical Arms Races, or Competitive Arms Races. Characterized by
competition for resources, esp. intraspecific. Examples: plants competing for light,
males competing for females
B. Asymmetrical Arms Races, or Antagonistic. Characterized by attack-defense
dynamics, esp. between species. Examples: predators versus prey, herbivores
versus plants, parasites/diseases vs. hosts.
C. Significance of arms races. Adaptation to other organisms, rather than the
environment, as the major driver of evolution?
The race: Individual predators and prey animals race against each other in a very real
sense: the predator is running to catch its dinner, the prey runs to avoid becoming dinner.
Both are literally racing for their lives. But there is also an evolutionary race between the
predator species and the prey species.
The evolutionary race: Some prey are faster than others. The slowest ones tend to get
eaten by predators. Kill by kill, the gene pool changes. As a result the prey species
becomes faster, and harder to catch. Because the prey is evolving to become faster, the
predator must evolve as well. Slower predators miss too many kills. They starve, or are
unable to compete for mates and territories with their faster, better-fed kin. Gene pool
changes and the predator evolves
This explains why ancient communities are so different from modern ones:
Carboniferous predators and prey were slow-moving, slow-witted, slow-growing. Selection
by predators on prey, and prey on predators, lead both to become faster. This dynamic has
been called an ‘arms race’ .
HUMAN ARMS RACES…
Arms Race: The term arms race refers to competition between two powers in the
development of weapons. Human arms races have gone on for thousands of years (e.g.
longbows versus knights at Hastings). But the concept became widespread due to the
extraordinary pace of advances in the 20th century, particularly WWII and the Cold War
Example: flight aircraft in the 20th century.
Inter-war Years: dramatic advances in fighter technology. The ability to rapidly pursue-
or run from- enemy aircraft was usually the deciding factor in combat
Faster aircraft were designed in the interwar years. The Spitfire had a powerful engine
(Rolls Royce Merlin), better streamlining (closed canopy, retractible landing gear), and
more efficient, smaller wings (designed by NACA, forerunner of NASA). But once you built a
faster plane, the other guy would counter - making a plane as fast or faster, and your
advantage was lost.
WW2: in an effort to keep up with and surpass the enemy, faster aircraft were designed.
The enemy, however, is not sitting still – far from it.
The other side counters: 1944 saw the introduction of the first jet aircraft by Germany-
far faster and more powerful than propeller-driven aircraft. A first-generation jet fighter.
Probably the best fighter of WWII— but too little, too late to tip the balance of the air
campaign. After WWII, the UK and US develop their own first-generation jets (Meteor and
Shooting Star, respectively)
The Cold War: fearing a showdown, NATO and Soviets keep upping the ante. Every time
one side improved, the other did as well.
Eventually, this comes to an end: record of 3200 km/hr set in the 1980s. Modern
fighter aircraft are actually slower than the aircraft they were designed to replace. Why did
, the race slow and then reverse?
(a) running up against the laws of physics (high drag at supersonic speeds)
(b) Spending on the contest conflicts with other needs (roads, doctors, universities)
(c) Other factors may become more important in the contest (F-22 is slower but stealthy)
This is a symmetrical arms race:
Basic idea:
• Each side competes for the same goal (e.g., control of the skies)
• They up their game, you up yours- move by one side leads to an identical move by the
other
• Leads to dramatic improvements in performance
• Eventually the arms race has to slow down or stop, because:
(a) Further improvement becomes difficult, or
(b) Increased spending on the contest conflicts with other demands, or
(c) other factors decide the contest
(other examples would include the the nuclear arms race in the late 20 th century, battleship
arms race in the early 20th century)
Studying human contests is useful because we know the history of these events, so we can
understand the processes that drive the patterns. Evidence from the modern world and the
fossil record suggests that strikingly similar dynamics occur in nature.
SYMMETRICAL ARMS RACES IN NATURE…
Organisms in nature fight over resources such as light, water, food, and mates. This leads
to arms-race dynamics
Evolution of forests as an arms race: Forests seem still and peaceful, but are actually
the result of an arms race. Why are trees tall? The most effective shape for a solar collector
should be a wide structure low to the ground - solar cells work perfectly well at ground
level, after all
Light competition: Trees fight for light. If you’re at the top of the forest, you get light. If
you’re below the canopy, you’re in the shadows. You want to grow up above everybody
else so you get the light, and they are stuck in the shadows. Modern forests are the result
of an arms race that has played out over hundreds of millions of years.
Arms race in plants: Fossil spores show that the first plants on land were liverworts and
hornworts, almost half a billion years ago. These are creeping plants. They spread out over
the ground to collect light- an efficient way to distribute light-collecting tissues. They fight
for light by creeping over the top of each other
The stem: a new technology advances the race. Mosses invent the stem: a vertical
column that supports photosynthetic tissue above everyone else. Now you’re above the
other guy, and he’s in the shadow. But once everybody has stems, what do you do? You
need to get even higher- but you start having trouble getting water and nutrients to the top
of the plant
Vascular tissue: higher and higher… Vascular plants have vessels: hollow tubes that act
as pipes to carry water and nutrients up to the top of the plant. Now plants can get tall
Early forests: competition for light gets fierce:- Huge amounts of material are
invested in building stems to compete for light in the Carboniferous (billions of tons of the
stuff is buried- this is the origin of Carboniferous coal deposits that fuel the Industrial
Revolution). These plants grow by stacking new material on top of old material- an
inefficient way to grow
Growth by stacking: Primitive plants stack up material to make a stem, creating a
cylindrical trunk. Early on, the stem is short and very fat – stronger than it needs to be
(wasteful). Later on, tall and skinny (dangerously weak). The stem is never really well-
designed at any point in the trees’ life
Annular growth: A sheath of living tissue- cambium- goes around the entire stem, under
the bark. Annually deposits new wood around the stem (tree rings). The tree can grow up
and out. Efficient use of material: thin trunk for young, short tree, fat trunk for old, tall tree.
Stronger shapes: tree is fattest at the base where the loads are highest.
