These Propositions are just that -- propositions. They are succinct, unhedged, and uncomplicated suggestions on various aspects of the world of the present, the past, and the future. Some of them are mild and uncontroversial, virtually self--evident, others could be regarded as outrageous from the viewpoint of a conservative soul. I am not claiming that all these propositions are "true" (for more on what "true" means, see NU017), and in fact they cannot all be true, as some of them (e.g. Propositions 12E and 12F on dinosaurs) are apparently mutually exclusive.
But I hope, at least, that they will provoke thought and perhaps some critical evaluation of their implications. Many of them have scope for setting up tests, for extrapolation, for prediction, in fact for running them through the whole gamut of objective probing which reveals the "truth" or otherwise of any scientific theory.
Where the Evidence Comes From
A word about sources and data. This suite of articles contains almost no new data, no astounding new results of trials. Some of the conclusions reached may be quite novel. But these conclusions are based on the most prosaic data, much of it available for many years in standard sources. A lot of the hard data quoted is taken from either the current (1989) edition of the Encyclopaedia Britannica, or from the Ninth Edition of this work, published in 1875. Some comes from the Guinness Book of Records!In fact probably half the evidence used in this suite of articles was already available a hundred years ago, and three-quarters available fifty years ago. Even the remaining 25% which has come to light more recently has been mostly in the nature of confirmatory detail, rather than some revolution in our views.
Hence the quotation at the head of this chapter. One of the side effects of this work will be to show that 'old' data can be reworked with success, like some mineral tailings, to reveal unsuspected new riches.
The Timescale of Events in this Suite Of Articles
It may be useful for the general reader if some background is given on the timescale of events which figure in this suite of articles.Almost all references will be to events which occurred many millions of years (my) before the present. Currently, the age of our entire universe is believed to be about 15,000 my; the Earth itself (and its satellite, the Moon) are believed to be about 5,000 my old.
Of course, life on Earth did not begin until a long time after the planet was formed (usually assumed to have been by condensation of gaseous material). An event occurred at around 600 my ago which was very obvious from the record of fossils found in the rocks. Before 600 my the rocks are almost empty of signs of life; after this time, rocks which were formed in a way suited to the preservation of fossils (say on the beds of shallow seas receiving a continuing load of sediments) may be crammed with fossils.
Fossils are often excellent indicators of the conditions which applied at the time and place where the creatures which left the fossil remains grew, and so they have been studied in great detail. Most of our knowledge of the geological past has been gained from fossils. So we have quite a good and detailed picture of events since around 600 my , and a much poorer picture of what happened before that.
The Ages of the Rocks
Table 1 shows how geological time is divided up; the different slabs of time can be regarded as layers of rock, with the youngest at the top. The time since abundant life has existed is conventionally divided up into three large sections, called Eras. These are, in order of increasing age, the Cenozoic Era, the Mesozoic Era, and the Paleozoic Era (these terms mean, roughly, the times of Young, Middle, and Old Life).| Age(my) | Period/Epoch | Era | ||
| 1 | 3 | Quaternary | ||
| 2 | 7 | Pliocene | ||
| 3 | 25 | Miocene | Cenozoic | |
| 4 | 40 | Oligocene | (Tertiary) | |
| 5 | 60 | Eocene | ||
| 6 | 70 | Paleocene | ||
| 7 | 141 | Cretaceous | ||
| 8 | 198 | Jurassic | Mesozoic | |
| 9 | 230 | Triassic | (Secondary) | |
| 10 | 285 | Permian | ||
| 11 | 350 | Carboniferous | ||
| 12 | 400 | Devonian | Paleozoic | |
| 13 | 440 | Silurian | (Primary) | |
| 14 | 510 | Ordovician | ||
| 15 | 580 | Cambrian | ||
| 16 | 4500 | Precambrian | ||
Each Era is itself divided up into smaller units called Periods or Epochs. The names of these units are shown in the table. Rock and fossil dating methods are now accurate enough so that the beginning and end of each of these Periods can be dated to the nearest my, in the younger rocks at least. A change from one period to the next is usually marked by a significant change in the fossil record, and in fact this change is fundamental, because it is usually the reason for splitting the record of the rocks up into different parts.
The oldest Period of all, that at the bottom of the Paleozoic Era, is called the Cambrian Period. It is in the oldest Cambrian rocks that the first signs of profuse, active life are found. The change is quite sudden. Something happened at the start of the Cambrian which greatly favoured the development and expansion of life on Earth.
Once it was thought that the Cambrian actually marked the first appearance of any form of life on Earth, and that the older rocks were completely devoid of fossils. More recently it has been shown that these older rocks, called Precambrian and extending back to the beginnings of the Earth itself, do in fact have some traces of life. Some of this life could be as old as 3500 my, but the evidence is not clearcut, and argument continues on the exact nature and age of this early life.
The actual figures quoted are subject to revision and refinement, but the general picture is clear. For seven eighths of its 5,000 my existence, the Earth was almost devoid of life. About 600 my ago, life burst forth in abundance.About 230 myago, a major change occurred, and about 70 my ago, another big change. Later in this suite of articles I will suggest some of the underlying reasons for these abrupt changes.
About Rock Types
This is not the place for a detailed explanation of the different types of rock, but there is one aspect of rock types which does have considerable relevance, and that is the distinction between 'continental' and 'oceanic' rock types.Both these rock types are 'igneous', formed by the cooling down of molten material. But the continental rocks, which form the bulk of the material of the Earth's present continents, are lighter in weight (and often in colour) than the oceanic ones and have a somewhat different chemical composition. They are also called acidic rocks, and granite is the most typical example
Oceanic rocks, also called 'basic' rocks, are heavier in weight and usually dark in colour. Basalt is a typical example. Oceanic rocks not only form the bedrock of all the major and deeper seas and oceans, they also underlie the continental rocks of the land masses. The situation has been represented as a continuous, solidified oceanic-rock 'sea' covering the whole of the Earth, with separate 'rafts' of continental material floating on this solid 'sea'.
In agreement with this picture, the continental 'rafts', which are usually 5-40 km thick, are said to be actually 'immersed' in the oceanic-rock sea, their bases extending below the level of rock in adjacent seabeds. And, in a classic Archimedes' Principle situation, the depth of immersion is usually greater under higher mountains such as in the Tibet region -- just as if the continents were really floating.
Naming Animals and Plants
Living creatures are identified by their 'scientific names', which consist of two parts, a genus name and a species name. For example, the walnuts are in the genus Juglans (from latin, 'Jupiter's nut'). The common walnut is Juglans regia (where 'regia' means royal). It is normal to print these scientific names in italics or underlined, and to have a capital for the name of the genus (plural 'genera') and a small letter for the species (plural 'species').Basically, a species represents the whole of a population which can interbreed. The genus is the next broader grouping, representing all those species which are believed to be closely related. Within a genus, interbreeding between species is sometimes possible (giving 'hybrids'), but not assured or common. The position is explained in rather more detail in Chapter 2.
Genera are themselves grouped into the next broadest division, the family. In plants, the names of these families usually end in '-eae'. The walnut family, the Juglandaceae, includes not only the true walnut genus Juglans but also Carya , the genus of the pecan and hickories, and others.
We have now painted a rapid picture of the Earth, its history, and its inhabitants, using a very broad brush. To continue this saga, we start by shrinking our focus right down, to look at a very minute part -- Rottnest Island.
NU002: How Plants Spread and Change
Version 1.0, printed edition ("Nuteeriat: Nut Trees, the Expanding Earth, Rottnest Island, and All That...", Planetary Development Group, Tree Crops Centre, 1989).
Version 2.0, 2004, PDFs etc on World Wide Web (http://www.aoi.com.au/matrix/Nuteeriat.htm)
Version 3.0, 2014 Sep 10, Reworked from Chapter 1 of "Nuteeriat" as one article in a suite on the World Wide Web.
Version 2.0, 2004, PDFs etc on World Wide Web (http://www.aoi.com.au/matrix/Nuteeriat.htm)
Version 3.0, 2014 Sep 10, Reworked from Chapter 1 of "Nuteeriat" as one article in a suite on the World Wide Web.