Saturday, December 20, 2008

Earth's Changing Habitability

(D'Souza on Evolution, Part 5)

We have seen in recent posts that the actual geological and fossil record does not support the idea that life's history has been represented by a single steady trajectory from simple to complex, that indeed the evolutionary paradigm is at every point falsified by the evidence. Nonetheless, there exist today living things (including humans) that didn't exist during earlier time periods. What's more, we think of many of today's organisms (again including humans) as more complex or more 'advanced' than earlier living things. If evolutionary explanations fail to account for this situation, what better explanation is there, or are we at a loss to explain the trend that impresses Dinesh D'Souza?

Fortunately, the results from a number of other disciplines--some of them unknown in Darwin's day--can be brought to bear on this question. These disciplines include astrophysics, chemistry, geology and paleogeology (and new models such as plate tectonics), climatology, and others. And the two-fold answer is, in reality, a quite simple one. First, the more advanced life alive today could not have survived the conditions that existed on Earth throughout the vast majority of its history. And secondly, all of the previously-existing lifeforms have played critical roles in changing the conditions of the planet and its atmosphere to make Earth habitable by the forms that live today, including humans.

To repeat, it is now clear that the land and seas of the Earth have been filled with life from the earliest possible moment, indeed from long before it would be expected according to naturalistic (and evolutionary) scenarios. Moreover, the conditions of Earth today--including such things as the ratio of land area to water area and the juxtaposition of the land masses (with respect to the planet's axial tilt)--are optimal for the maximum biomass and the maximum diversity of life! On any objective view, everything about the Earth is designed for life, and the actualization of life has been the striking characteristic of Earth's history.

But what is also clear is that the Earth's conditions have been (throughout its prior history) drastically different than they are today, and that in a number of ways relevant to the question we've been examining. This discussion may only scratch the surface of these differences (as scientists are only beginning to understand many of the conditions of earlier periods in Earth's history).

The Earth's rotation is slowing down (due to ongiong gravitational interaction with both the sun and moon). In earlier periods, the rotation period was far shorter than 24 hours. This means that day and night were much shorter and that what we consider hurricane-force winds would have been constant, and that when winds were less than 100 mph at ground level, they might have exceeded 2000 mph at six feet above the planet's surface. At the same time, the Earth's luminosity--and thus, the amount of heat reaching the Earth--was much less. Except for single-celled life, Earth was indeed a very inhospitable place for the first four billion years.

Of course, life itself had little to do with slowing down the planet's rotation rate. But other characteristics of the early Earth--conditions inhospitable for advanced life--were improved by the earliest life. A short list of things essential to birds and terrestrial mammals (including humans) that 1) were not present (or not present in life-friendly concentrations or forms) or necessary for 'simple' life and that 2) are as they are today largely as a result of the existence (for billions of years) of those earlier life forms includes: an oxygen-rich atmosphere, a protective ozone layer, topsoil, and trace elements (life-essential but toxic in other quantities or form). Other by-products of eons of life history that are necessary for a technological humanity include limestone, coal, oil, and natural gas.

In short, the trend toward 'more advanced' life, far from supporting an evolutionary explanation for life's history is much better understood as the careful design of the planet by its Creator to make it maximally suitable for the greatest diversity and abundance of life throughout its history, culminating (in these recent times) with the most advanced life, including technologically-advanced humans capable of understanding the Creator's purposes for the universe.

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