Evolution of Intelligence
In class exercise:
In 25 words or less, write down your definition of what constitutes
Put your definition on the table in the front of the room.
Food/crop/plant production is
very sensitive to climate; many zones exist
Climate results from the uneven distribution of heating over the
surface of the earth caused by the earth's tilt. This tilt is
the angle between the earth's rotational axis and its orbital
plane around the sun. Currently this angle is 23.5 degrees.
Long term climate is also affected by the heat balance of the earth
which is driven mostly by the concentration of CO2 in
Climate change can result if the pattern or solar radiation is changed
and/or if the amount of CO2 changes. There is abundant
evidence that the earth does undergo climatic change. Climatic
change can be a limiting factor for the evolution of many species.
Effects of Ice Ages
- Periodic Ice Ages - Glacial-Interglacial Periods
We currently are nearing the end of a small, minor interglacial period
Major Ice Ages: Most of the Planet is Covered
Minor Ice Ages: 40o Latitude and Above. The most
recent one of these occurred about 15,000 years ago and the
coverage of the ice sheet is shown here
Little Ice Age: (1000-1850 AD; Irish Potato Famine; Nisqually Glacier)
Causes of Ice Ages
needs to be PERIODIC!
Changes sea level by 100 meters exposes continental shelfs
changes continental shelf composition due to increased deposition
changes hydrological cycle through less evaporation
changes landscape Great Lakes; Seattle; Stoss and Lee
Changes drainage patterns
changes topsoil characteristics
massive flooding episodes Eastern Washington
Solar Cycle no evidence
Volcanic Dust in Atmosphere why periodic?
CO2 Cycle why periodic? factor 2 reduction
causes 7 F drop Record of CO2
and temperature variations
Increased precipitation at poles due to changing orientation of continental
Changes in mean temperatures of ocean currents what mechanism?
The most Probable Cause:
Orbital Variations of the Earth!
- Eccentricity variation 90,000 years 5 variation
around mean value. This is due to Jupiter.
- Change of tilt of axis 24,000 years
More About Ice Ages
Let's Melt the Polar
Intelligent Life on the Earth
Evolution of Intelligence:
- We know little about this
- We do know that the brain size of mammals has slowly
increased over geologic time
- Brain size is proportional to body weight
Define Relative Intelligence:
- Amount of brain tissue in excess of that required for basic
- This is known as Encephalization level (EL)
- P = body mass; EL is basically measured by K
- K can be recovered from the fossil record to some extent
What is Intelligence?:
- Biological Intelligence: environmental conditions determine the
rate of growth of intelligence
- Artificial Intelligence: number of neurons basically correlates with
The point of this scale is one of RELATIVE intelligence there is
nothing absolute about it.
Causes of Mass Extinction (Dinosaurs/Plankton)
Clearly are the result in reducing the amount of sunlight that
reaches the surface.
Possible Mechanisms of Extinction
What do we know about the last extinction event 65 million years
- We know there was an impact event
- The impact site was the Yucatan Penisula
- We know the dinosaurs became extinct at this time
- We know that much of the plankton became extinct
But we don't know the causal connection between the impact and
the extinction cycle but clearly something basically put a halt
to photosynthesis for some period of time.
Possibilities for blocking out the sunlight:
Clouds that Persisted? this is a recent theory, perhaps
somewhat farfetched. There might also be a component of acid rain from
this event that could have harmed much of the plant life that large
plant-eaters fed on.
- Dust ejecta from the impact problem is that the residence time
of dust in the atmosphere is fairly short
- Soot from global forest fire induced by the impact this is
more promising as soot is very fine particulate matter that will find
its way to the strasophere where the residence time is long
When will the next mass extinction event happen? (one of course
could argue that its happening now)
Sometime in the next few 10's of millions of years the earth is
likely to be hit again but an object 10--100 kilometers in diameter.
Learn More about
NEAR EARTH OBJECTS
Intelligent Life on the Earth
What Can we Conclude from the Above Graph:
- Increase in Relative EL exhibits a well defined pattern
over the last 200 million years
- Fastest growth was from 600--250 million years ago when species
first emerged on the land
- Mass extinctions clearly are important as they substantially
alter the rate of growth
- Unaltered rate would have produced current human level of EL
about 60 million years ago
- Continental rate is much higher than the oceanic rate
- Smooth extrapolation backwards from last few million years of
continental data suggests it takes 20 billion years for intelligence
It seems likely than when terrestrial ecosystems developed, the flow
of nutrients to the oceans became impaired which served to suppress
that ecosystems growth rate over the rest of geologic time.
Factors that might contribute to rate of growth of intelligence:
- Temperature: Many species function/learn best in a constant
temperature environment. Large temperature variations are then not
conducive to learning (this applies mostly to reptiles)
- Time - clearly EL evolves slowly upwards with time. Doubling time
appears to be about 2 million years
- Biogenic Environmental Diversity the more diverse the ecosystem
the more competition for scarce resources (food) there is could be
strong environmental stimulus for growth of intelligence. Suppression
of diversity by environmental disaster, climate change, or nutrient
depletion would then reduce this growth
- Trophic Level is important where you are in the food chain
does this favor growth in predator or prey?
- Adaptation: Species defense mechanisms are a signature of of
evolution of intelligence. For instance, Coral defends itself statically
but glue-secreting frogs have ingenious method for fending up predators.
- Metabolism: large metabolism of mammals demands larger brain and
hence establishes initial capacity for evolution of intelligence in mammals
But clearly the role of mass extinction is paramount and allows the
survivors to fill the newly opened ecological