19. A better way to the answer

Now that we have our three root issues—the intrinsic, the extrinsic and their relations—we must find a way to describe Darwin’s variations, his competition, and his natural selection so that they can become rigorously quantitative, and allow for an unambiguous solution through data. If we want to properly quantify the Darwin solution, then we must surely address these three issues of (a) what biological populations do intrinsically, simply by being biological; (b) what they do extrinsically, and purely in response to the environment; and (c) what they do due to the interaction between these. Can the problem Darwin attacked be rephrased so it can be approached differently and in light of our recognition of these three factors: the intrinsic, the extrinsic and the relations between them? But since this is science, we must find them in action in some representative population or species.

Figure 16: Competition & Natural Selection
 Competition & Natural Selection

We can take again Joule as a guide. Figure 16 is a representation of our Brassica rapa experiment. In the fashion of Joule, we tried to isolate our three factors. He used a water bath to keep his environment constant, while we maintained a consistent and non-variant light and water supply. We then observed all plant responses in mass, energy and numbers.

As on the right in the figure, a thought experiment after Joule is immediately possible. It has reference to the intrinsic and the extrinsic: we change (in this case double?) the amounts of light and water presented to the plants; we again measure the results; and we then determine whether or not they can produce the same equilibrium age distribution, or whether they somehow revert to some other state.

But this is then simply a matter of how the environment is interpreted once the data is gleaned. If the entities attain the same state when we change these external factors, then the environment is of little real short-term consequence to their fundamental definition as a species … which is what Darwin asserts. He insists that we only see the effects of his variations over the long-term. Populations can in other words cope with most short-term variations because they have a standard point of reference, as a species, around which they oscillate. It is surely only a matter of determining the correct mathematical approach to that data to ascertain if it supports the steady state of the exponential law; the steady state of an equilibrium age distribution population; or of some other yet-to-be-determined steady state. It should also be possible to examine the extent of all variations, and suitably apportion them. But … this is mathematically quite straight forwards. It is the domain of partial differential equations. We need only find the correct equation, and we will immediately have our partial differentials.

The main issue is, of course, whether or not our three issues are even in principle isolable and/or relevant; and if they are, whether or not they can help us identify the boundaries we need for without a suitable boundary we cannot proceed. Our problem, then, is how to draw a boundary around a biological population so we can isolate the intrinsic and the extrinsic, and measure Darwin’s natural selection and competition.

In the early 1950s the British field researchers Richards and Waloff conducted a five-year field study in Ascot, Berkshire, United Kingdom, on the cricket or grasshopper Chorthippus brunneus, a member of Acrididae, and a semelparous annual (Richards & Waloff, 1954). As we did with Brassica rapa, they recorded ages, masses, and population numbers … although they did not record energy values. But again as with our B. rapa population, Richards and Waloff saw the population increase, collapse under environmental stresses (due to variations in sun and rain), and then recover. Yet unlike ours … their environment varied and was uncontrolled. Ours was kept rigidly controlled, theirs uncontrolled. But the end result was the same, so again raising these issues of the intrinsic, the extrinsic, their relations, and the boundary to be drawn to isolate them. The crickets oscillated around a definite equilibrium age distribution population.

Whether biological populations do or do not follow the exponential law, the data presented in Table 2 for Chorthippus brunneus again allows an equilibrium age distribution population to be calculated. What, then, is the environment’s true role—extrinsically—as against factors intrinsic to each population, and that each population seems to utilize as it heads towards an equilibrium age distribution?

Table 2: Data for Chorthippus brunneus; member of Acrididae
 

Year

Season

Stage in cycle

Numbers produced

Average mass (mg)

Days lived

 

1947

Autumn

Adults

1,200

148.2

42

Generation I

   

Pods

4,006

47.0

188

 

Winter

Eggs

44,063

4.0

209

1948

Spring

First Instar Nymphs

3,513

5.1

27

   

Second Instar Nymphs

2,529

11.3

25

 

Summer

Third Instar Nymphs

1,922

31.6

28

   

Fourth Instar Nymphs

1,461

65.8

32

 

Autumn

Adults

1,300

148.9

44

Generation II

   

Pods

2,432

40.3

186

 

Winter

Eggs

22,614

4.0

207

1949

Spring

First Instar Nymphs

16,620

5.1

28

   

Second Instar Nymphs

14,958

11.4

26

 

Summer

Third Instar Nymphs

13,462

32.8

29

   

Fourth Instar Nymphs

7,000

70.7

33

 

Autumn

Adults

3,500

137.6

43

Generation III

   

Pods

9,976

44.3

191

 

Winter

Eggs

111,728

3.7

212

1950

Spring

First Instar Nymphs

48,191

4.8

27

   

Second Instar Nymphs

25,541

10.4

25

 

Summer

Third Instar Nymphs

13,592

28.6

28

   

Fourth Instar Nymphs

5,233

58.3

33

 

Autumn

Adults

2,250

107.3

39

Generation IV

   

Pods

1,269

25.9

191

 

Winter

Eggs

10,406

2.9

212

1951

Spring

First Instar Nymphs

1,700

4.0

25

   

Second Instar Nymphs

1,496

8.8

23

 

Summer

Third Instar Nymphs

1,302

24.1

26

   

Fourth Instar Nymphs

1,148

49.2

30

 

Autumn

Adults

1,090

122.3

49

Generation V

   

Pods

1,483

27.5

170

 

Winter

Eggs

11,274

3.3

189

The biology and ecology of the bristlecone pines of northern California, Pinus aristata and P. longaeva give us further—but only qualitative—information to state our case:

Two species of bristlecone pine exist. … Though growing only 160 miles/260 km apart, those found on the high ridges of the Great Basin country (extending from the eastern border of California, across Nevada to Utah) reach the greatest age. The Rocky Mountain bristlecone pines (Pinus aristata), which reaches ages of up to 1,500 years, are to be found in an area that extends from the eastern slopes of the southern Rocky Mountains in Wyoming through Colorado and down into New Mexico. The environment in which the bristlecone pines live seems an unlikely place in which to find trees of such antiquity. In fact, it is the very harshness of this environment, and the bristlecone’s response to it, that has enabled this tree to achieve such great age.

The Great Basin bristlecone pines grow on steep, rocky slopes between approximately 9,000 ft/2,700 m and 11,500 ft/3,500 m. Between November and April each year, temperatures plummet to well below freezing and the area may receive 9 ft/2.7 m of snow. These conditions are exacerbated by the ferocious winds that scour the mountainsides. The bristlecone pine has adapted by lengthening its growing season and by putting on new growth when temperatures are much too cold for other plants.

Most of the trees are under 30 ft/9 m tall, and much of their wood—on the windward side at least—is dead. The sparse crowns of twisted and contorted branches are supported only by narrow strips of living wood. Their ability to live in nutrient-poor soils and to conserve water has been vital to the survival of the bristlecone pines. The tree has developed special waxy leaves (needles), which may not be shed for over twenty years, thus helping to reduce evaporation and conserve moisture; it also contains high levels of resin, which acts as a wood preservative and which is exuded to form a waterproof layer over any exposed branches. To maximize water-absorption, the tree also has an extensive network of shallow roots.

It is interesting to find that the average age of the bristlecone pines on south-facing slopes in the White Mountains is typically around 1,000 years, whereas on north-facing slopes the average age rises to over 2,000 years. Entire groves of trees that are over 4,000 years old stand on the north-facing slopes, and it is amid one of these groves that the ancient Methuselah tree is found. The appearance of bristlecone forest on north- and south- facing slopes is markedly different. While the southern slopes have many healthy-looking trees, covering the hillside in quite dense forests, north-facing slopes contain trees that are much more widely spaced, squat and gnarled, with many dead branches. The severity of the environment on the north-facing slopes causes the growth rings to be more tightly packed, which in turn makes their timber more durable and the trees more long-lived. The durability of the timber is so exceptional that scientists have found dead wood, which has been shown to be 7,000 years old, lying intact close to living trees.

A forest consisting of trees that are thousands of years old can afford to regenerate at a leisurely pace. Only a handful of new seedlings needs to germinate successfully each century to ensure the forest’s survival. Bristlecone pines tend not to live in isolation, but to form communities with plants such as the sage brush, mormon tea, and mountain mahogany. Birds such as the mountain blue bird, the chickadee, and Clark’s nutcracker feed on their seeds. The last is most important for the bristlecone pine’s regeneration, because it collects seeds and buries them in caches in the soil, thus helping the seedlings to gain a foothold in the inhospitable terrain (Lewington & Parker, 1999, pp 35-37).

The above analysis not only underscores the issues Darwin highlighted, but provides us with valuable ammunition by drawing attention to our three issues of intrinsicality versus extrinsicality, the various proportionate contributions, and how these interconnect through populations in the manner of Darwin by presenting a response to a steady state, or lack thereof, and howsoever caused or not caused.

We can again observe our three suggested roots of Darwin’s natural selection by a different analysis of this same species—which again discusses the nature and effects of constraints, and so the intrinsic versus the extrinsic, and whether or not a steady state arises, and if so for what reason:

“… the oldest pines have in a certain sense been dying for two millenniums or more. They now possess only a narrow strip of their once complete bark and the growing tissue beneath it. True, the dying-back of this life-line is exceeding slow, and several of them seem good for at least five centuries still …”. Dr. Edmund Schulman, Discoverer of ‘Methuselahs Walk’, in the National Geographic …

When Schulman began his study of bristlecone pines (Pinus longaeva) people still believed that the biggest trees in the world, the giant sequoias, were also the oldest. Thousands of giant sequoias had been felled by the loggers, and in many cases the rings could still be easily counted all the way to the centre (the wood is almost rot-proof), dating some trees over 3000 years old.

Schulman made his amazing discoveries in the mid-1950s. Using a Swedish tree-borer, three feet long and only the thickness of a pencil, he took a series of radial cores from the bristlecone pines. Then, in his laboratory, he counted the tree rings under a microscope. Seventeen trees proved to be over 4000 years old and still alive—in a fashion.

Paradoxically, Schulman found no link between the size of the ancient trees and their age. Instead, longevity in trees seemed linked to stress. … The oldest bristlecone pines have chosen the most stressful climate imaginable: in winter buried in snow or wind-blasted by ice crystals, in spring and summer parched by the sun, with nothing to drink except melting snow, and only a few weeks when growth is possible. So stress slows down the tree’s clock to the absolute minimum necessary for life (stress does the same for the bonsai, but by forcing the bonsai to produce juvenile roots and shoots it would supposedly make it immortal). In fact, the oldest bristlecones live in the twilight between life and death. The main trunk dies several thousand years before the last of its branches, whose life finally hangs by a thread—the thread of bark attached to the roots.

Schulman’s advances on the frontiers of dendrochronology (he and his successors sampled 9000-year-old dead wood here in the White Mountains) gave a serious jolt to archaeologists as it proved they had wrongly calibrated the scale for carbon dating by hundreds of years. (Pakenham, 2002, p. 73-74).