The Big Ratchet: How Humanity Thrives in the Face of Natural Crisis (31 page)

    
22
   
It sputtered:
Kass and Yung 1995.

    
22
   
Angle of 23.5 degrees:
Laskar et al. 1993.

    
23
   
Other celestial bodies:
Touma and Wisdom 1993. Venus’s axis swung upside down at almost 180 degrees, aiming the poles nearly parallel to the sun, so in summer the pole is hotter than the equator. Mars’s two moons do not have large enough mass to keep the planet’s tilt stable.

    
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Atom to complete the cycle:
This weathering cycle was first described in the 1980s by Walker et al. (1981).

    
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Millions of years hence:
This quotation is the last line of Chapter 1 in Hutton (1795).

    
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That we cannot live without:
Cardinale et al. (2012) and Naeem et al. (2012) discuss the functional roles of biodiversity.

    
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And an empty plate:
Cardinale et al. (2012) provide an overview of the state of knowledge about the functions of biodiversity.

    
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Visible with a microscope:
A species is generally defined as a group of organisms capable of breeding and producing fertile offspring. The concept does not always stand up to the realities of the world. Seemingly distinct species of Galapagos finches, as a case in point, have been known to mate and produce fledglings (Grant and Grant 2010).

    
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Ratcheted up a notch:
Szathmary and Smith (1995) discuss the major evolutionary transitions.

    
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Precursors for life:
Schopf and Kudryavtsev 2012, 35.

    
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From the Earth’s interior:
The simplest forms of life that lived in sulfur swamps used hydrogen from the hydrogen sulfide in the swamps and the sun’s energy to form sugars as their food in an early form of photosynthesis.

    
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Photosynthesis was a disaster:
The new process also converted the sun’s energy and ubiquitous carbon into sugars, but this time water played a starring role. Instead of hydrogen sulfide to supply the hydrogen, water could do the job. With a new machinery to split a molecule of water into its components, hydrogen and oxygen, photosynthesis could occur wherever there was water, sunlight, and carbon from the air. Photosynthesis using water could occur anywhere on the Earth’s surface where water could be found, rather than remaining confined to swamps with a source of hydrogen sulfide.

    
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Cancer-causing ultraviolet rays:
Photosynthesis with water left oxygen as a by-product. At first, the spare oxygen bonded with iron dissolved in the ocean. The new minerals sank to the ocean floor and eventually became the first signs of rust banded in rocks. Around 2.5 billion years ago, the iron was used up. There was nowhere else for the oxygen to go but into the atmosphere, which led to the formation of the ozone layer.

    
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Fish, insects, birds, and mammals:
The evolution of sponges, jellyfish, corals, and flatworms marks the Cambrian Explosion. Some biologists attribute the explosion to the atmospheric oxygen that enabled larger body sizes to develop as oxygen allowed for efficient conversion of food to energy. Others point to the opportunities for new niches created after a collision with a comet or some other calamity wiped out most forms of life.

    
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Over time became distinct species:
The process of new species forming as continents spread is called allopatric speciation. With the increase in distance caused by the movement of tectonic plates, mountain ranges, and other geographic barriers, a once-united species can split into distinct groups. If individuals from the two isolated groups cannot mate, over time each will adapt to its own condition and they will become two distinct species. This
is how kangaroos, koalas, Tasmanian devils, and other marsupials came to be the dominant type of mammal in Australia. About 130 million years ago, many mammals lived on the supercontinent called Gondwanaland. As plate tectonics split Gondwanaland into two separate landmasses, different types of mammals emerged on each plate (Springer et al. 1998). Marsupials, mammals in which mothers carry their infants in a pouch, thrived on the isolated continent of Australia. Only one marsupial evolved from the common ancestor in South America: the opossum.

    
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A new niche or a new source of food:
The process of individuals mating with others nearby to exploit new niches or sources of food is called sympatric speciation. Individuals might be more likely to mate with another nearby in places where the food, temperature, soil, or water is slightly distinct from those further afield. Over time, new species can emerge even without large geographic barriers. This is what may be happening to apple maggots that squirm into the fruit (Feder et al. 2003). Female apple maggots prefer to lay their eggs on the familiar fruit where they were born, and males seek mates on the type of fruit where they were born. When immigrants brought domestic apples to America in the nineteenth century, the apple maggots had more options. They could lay their eggs either on the fruits of the native thorn-apple tree or on the introduced domestic apple. Since then, the thorn-apple maggots and the domestic-apple maggots have been in the process of separating into distinct groups. This textbook example of speciation is reported in Forbes et al. (2009) and Jiggins and Bridle (2004) and in the sources cited in these papers.

Chapter 3: Enter Human Ingenuity

    
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“. . . [S]urvive for many years:
Quoted in Cavell 2009, 25. “Esquimaux” was the term used at the time for native peoples inhabiting the Arctic.

    
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100 pounds of pepper:
The amounts of these and other provisions for Franklin’s expedition are listed in Appendix 1 of Cookman (2000).

    
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Her missing husband:
The Admiralty sent several search parties with little success. In 1854 an Arctic expedition led by John Rae brought news of the “mutilated state of many of the corpses,” with reports “that our wretched countrymen had been driven to the last resource—cannibalism—as a means of prolonging existence.” John Rae is quoted in Cavell (2009), 31.

    
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“. . . [C]an live there also”:
McClintock 1861, 13.

    
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“. . . [E]nforced by public opinion”:
Quoted in Richerson and Boyd 2010, 6.

    
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“. . . [H]is cultures are born”:
Dobzhansky and Montagu 1947, 590.

    
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“. . . [T]hings that genes can’t!”:
Richerson and Boyd 2005, 7.

    
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Beak size they’d inherited from their parents:
This fascinating response of finch beak size to climatic variability is documented through the long-term work of Rosemary and Peter Grant (1993) on the Galapagos Islands as well as many other publications.

    
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Pulled a rope:
Plotnik et al. 2011.

    
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With a harsh “kaw”:
Cornell et al. 2012.

    
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Not be worth the investment:
Potts (2011) reports that the brain consumes approximately 65 percent of a baby’s total energy requirement and 20 to 25 percent of an adult’s, even though brain tissue makes up only 2 percent of an adult’s body mass.

    
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Life-span of the animal:
Mathematical arguments for the evolution of individual learning, social learning, and culture in relation to variability in the environment are made by Boyd and Richerson (2009), Enquist and Ghirlanda (2007), Henrich and McElreath (2003), and Strimling et al. (2009).

    
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Macaque’s complex social behavior:
The history of the study of Japanese macaques is documented in Yamagiwa (2010).

    
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Fish for their next meal:
Other examples of cultural diffusion in nonhuman species include the spread of lobtail feeding on humpback whales (Allen et al. 2013) and the adoption of social foraging norms in vervet monkeys (van de Waal et al. 2013).

    
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Process information, make it possible:
Holloway (2008), and Blazek et al. (2011) describe brain evolution as the increase in brain size and the creation of more complex brain structures in the cerebral cortex.

    
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Climatically noisy Pleistocene:
Potts 2011.

    
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Interacted at different times:
The interplay of factors is put forward in Holloway (2008). Other primate and bird species show relationships between brain size and learning (Reader and Laland 2002; Sol et al. 2005).

    
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Less energy gets consumed in the process of digestion:
Wrangham 2009, 43.

    
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Digestive tracts and large, learning brains:
The argument of the social-intelligence hypothesis is from Aiello and Wheeler (1995), Reader and Laland (2002), Herrman et al. (2007), and Navarrete et al. (2011).

    
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Few parents would dare:
The story of the Kelloggs is described in Henrich and McElreath (2008).

    
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Monkeys, chimpanzees, and children:
Dean et al. (2012) conducted this experiment.

    
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Ground with a slender stick:
This and other examples of cumulative technology in apes are given in Pradhan et al. (2012).

    
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“. . . [F]orms of social transmission”:
Richerson and Boyd 2005, 5.

    
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Direction of natural selection itself:
Laland et al. (2010) and Fisher and Ridley (2013) review gene-culture evolution and how it has shaped the human genome.

    
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Thirty-five out of every hundred people:
Gerbault et al. (2011) describe the evolution of lactose tolerance.

    
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Tree-climbing African ancestor:
Recent genetic evidence suggests that the divergence between wild apes and humans occurred earlier than previously reported (Langergraber et al. 2012).

    
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Approximate dates for the evolution (graph):
Dates from the Smithsonian Institution’s interactive page at
http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive
, entitled “What Does It Mean to Be Human?” 47
Other species in the human family:
The term “human family” is used here to mean species in the genus
Homo
.

    
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One-ninth that of
Homo erectus
: Sources in the literature ascribe varying dates. This information is from deMenocal (2011), Potts (2012), Stewart and Stringer (2012), and the Smithsonian Institution’s interactive page at
http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive
, entitled “What Does It Mean to Be Human.”

    
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Olduvai Gorge in northern Tanzania:
Semaw et al. 1997.

    
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3.4 million years:
McPherron et al. 2010.

    
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Gombe National Park in the 1960s:
A precise definition of a “tool” is elusive. A widely used definition from Beck (1980) is the use of an object “to alter the form, position, or condition of another object, another organism, or the user itself when the user holds or carries the tool during or just prior to use.” This definition does not include equally complex behaviors, such as nest-building, or spitting water jets to dislodge insects (Bentley-Condit and Smith 2010, Seed and Byrne 2010, Brown 2012).

    
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Sticks to spear prey:
See Seed and Byrne (2010), Boesch et al. (2009), and Bentley-Condit and Smith (2010).

    
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To break their shells:
Rutz and St Clair 2012.

    
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Tool use exploded:
Diamond 1997.