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 | From Darby's online text:
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EXPLAINING HOW LIFE WORKS - DISTANT HISTORY |
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Human beings have an innate need to understand things, it's how we learn and how we teach - just try to teach something that you really don't understand! In explaining things that are difficult to grasp, we have a long history of using what we do sort of know to explain what we really don't.
There are other ways to look at this, but one possible view of human history is that we see Nature in the terms that make the most sense at a given time. Older societies, without the technology to strongly affect their worlds, saw their world in terms of the things with Power: Nature Spirits, with motivations one might expect from a fusing of human consciousness but the limitations that come from being wind, or forests, or the sun above. Later, as humans gained the ability to manipulate their own environment, as power over Nature became something in their grasp, the forces of Nature they believed in became much more human, in form and personality, although much more powerful - the human gods controlled those larger aspects of the world the way that humans controlled the small aspects of theirs, and animal spirits became more human and less powerful. Today, these explanatory ideas occasionally slip out of the realm of explaining Nature and becomes something more concerned with Human Nature, with those aspects of Life and Afterlife that still seem unexplainable, and the forces conceived are less human and more forces of Consciousness itself. Meanwhile, centuries of small successes in explaining this or that piece of the big Nature Puzzle has moved humanity, or a sizable fraction of it, from seeing Nature as something that can not really be understood, that must be explained in supernatural terms, to the conviction that everything can be broken down into tiny bits and all of the workings analyzed. We like the feeling that this has moved us somehow closer to the Truth, and Scientists probably feel some of the same sense of Specialness that used to be the province of priests, of being more In The Know than the rest. Are we closer to some knowable Truth?
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BUILDING UPON KNOWLEDGE FOUNDATIONS |
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When we look back from today to ancient times, there's no reason to think that human beings were any simpler or stupider as a group or as individuals than they are today. They did have a much smaller pool of accumulated knowledge to build upon, so you might say that they were ignorant.
But certain aspects of humanness were undoubtedly just as powerful then as now: the need to know why things happen the way they do, and the need to break information down into manageable and useful bits, and the need to categorize and explain relationships. Of all the abilities humans have in different amounts than other animals, it may the the greater sense of how cause relates to effect that most is the basis of science.
You can see aspects of human organization in how people have investigated Nature - we look for family, tribe, and nation types of relationships, in patterns that match patterns in human societies. If Modern Science is a product of "Western Society" - which is arguable, of course - it may just be an outgrowth of the level of structure and coordination and planning needed for continents of cities and support infrastructure to interact meaningfully with a globe of trade.
Historically, early biology was a mixture of a need to understand the practical - humans have shown a practical grasp of genetics millennia before Mendel began to work out the details - and a compulsion to grasp the Big Picture. From a simple level, as the concept that a dog, a wolf, and a fox were different types of animals but could be joined together in a larger but definable type of Canines, to a larger but understandable concept that living things with similar functions could be placed in groups together - the creatures of the water, the creatures of the air, the slithering legless things, the things that grow from the ground, et cetera. It seems a simplistic way of grouping things together, but one suspects that it was convenient, and that the ancients who really used the system probably realized that it had some limitations, as systems users today do.
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Carl von Linne, a Swedish botanist (plant scientist) known as Carolus Linnaeus (Latin was the common language for European science, so writings and often names were Latinized) began work in 1735 on a system that would organize descriptive classification from the smallest of related groups up to the very largest. The system he developed, with revisions, is the basic system still used today to systematically organize types of living things with their relatives. The basic structure was similar to how human organizations work, with groups-contained-within-groups, be they feudal power structures or military organizations. Each particular type of living thing would be designated a species (from the same root word as "specific"). Closely-related species could be collected within a larger grouping, a genus; related genera are grouped into a family, families into an order, orders into a class, classes into a phylum, and phyla into a Kingdom, the biggest and most general group. In Linnaeus' time, there were just the Animal Kingdom and the Plant Kingdom, but later discoveries have convinced some biologists that some distinct types of organisms, such as Fungi and some tiny single-celled organisms, should be given their own separate Kingdoms.
Some subdisciplines of biology use a basic Linnaean type of taxonomy, but may change the basic names used for a few of the groups. Commonly, for instance, plant and fungus taxonomy uses the term Division instead of Phylum.
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HUMANS |
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KINGDOM: Animalia
PHYLUM: Chordata
SUBPHYLUM: Vertebrata
SUPERCLASS: Gnathostomata
CLASS: Mammalia
ORDER: Primata
SUBORDER: Haplorhini
FAMILY: Hominidae
GENUS: Homo
SPECIES: Homo sapiens |
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YELLOW MOREL MUSHROOM |
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KINGDOM: Mycota
PHYLUM / DIVISION: Eumycota
SUBPHYLUM / SUBDIVISION: Ascomycotina
CLASS: Dicsomycetes
ORDER: Pezizales
FAMILY: Morchellaceae
GENUS: Morchella
SPECIES: Morchella esculenta |
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As you might see from the examples above, the system is a little more complicated than it sounded. Sometimes, two or more groups are found to be more closely related than anyone thought; they might be connected as supergroups ("super-" put on a group name). And sometimes a group is not as unified as was thought, and is split into subgroups.
Biology, like the sciences in general, is produced by human beings who often disagree with each other's ideas and fight over what the "proper" labels should be. For the most part, it is perfectly allowable for someone to say that this or that group should be a subphylum rather than a phylum, or a family rather than an order (this will come up later in the discussion about Kingdoms). However, what is not allowed is to, on a whim, change the name of a particular group - you can't say, "I don't like the genus Ursus for bears, I and everyone I work with are going to use Yogi from now on." Once a group is named and the name accepted, it may be tossed about on the "classification ladder," but one must gain a broad consensus and acceptance before a group's actual name is changed. If one book places sponges in their own Kingdom and one puts them in a phylum, in both cases the group will have the name Porifera; this limits confusion when doing background research on organisms.
Another set of rules, called binomial nomenclature (2-name naming), determines how species names are used. You'll see in the examples that species names are two words: a capitalized genus name and an uncapitalized specific. The second word has no meaning by itself, and is never capitalized, not even if a proper noun is used as the source of the term. Species names (and Genus names) are also treated as foreign words in English, meaning that they are italicized or underlined when printed or written. The names of other taxonomic groups are often not italicized or underlined, but that usage seems to vary.
Typically, species names are abbreviated by making an initial of the first word and spelling out the second - you may be familiar with E. coli, the abbreviated name of Escherichia coli, a common intestinal bacterium that, if introduced into an incompatible intestine, can cause food poisoning.
Deciding what living things should be classified in the same groups requires deciding what's related to what, and how close those relationships are. Long ago, it was often done by lumping together analogous traits: features used to do the same function. This is why, in Biblical times, if they had fins and swam ("Beasts of the Water"), or wings and flew ("Creatures of the Air"), they belonged in the same groups. By this approach, long wiggly things like snakes would be grouped with earthworms and eels.
As more and more people studied Nature in detail, it became obvious that a butterfly's wings were very different structures than a bird's wings. And sometimes, it could be seen that two structures used for very different functions - such as a human hand, a bat's wing and a whale's flipper - all contained the same internal architecture, with sometimes subtle changes in internal parts producing the outward changes. Traits with similar internal structure are called homologous traits, and it was eventually decided that these traits were a better measure of relatedness than analogous traits. Keep in mind, however, that traits can be both analogous and homologous (like a monkey hand and a human hand), it isn't automatically an either / or situation.
One modern approach to classification is very focused on critical traits that arise and characterize a new family line - histories are based upon the period in the past that such traits arise. This approach is called cladistics.
Much basic taxonomy is still done anatomically, although the level of detail has gotten smaller through the use of microscopes and broader through the discoveries of genetics and biochemistry (yes, molecules have a sort of anatomy). These will be covered later as they come up in the historical journey.
The original two Kingdoms were Plantae and Animalia, which remained the only Kingdoms until the middle of the 20th Century. During the last 40-50 years, those groups have been splintered a bit - Fungi was split off from the plants, Protista removed the single-celled eukaryotes (and the problems of their often-combined characteristics) and Monera was made for the prokaryotes. Those five Kingdoms were considered "the" Kingdoms in most basic biology books, even though the splintering has continued. The latest basic books now recognize a sixth group, the Archaea, once thought to be odd monera / bacteria but now considered a fundamentally different group.
Many advanced systems (mostly in the plant and microbe areas) add a Domain level above the Kingdoms; most commonly, there are three domains. The Monera and Archaea (see below as Kingdoms) are Domains, with the rest of the Kingdoms in the Eukaryota.
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The modern definition of classification groups depends upon each species in the group evolving from a single ancestral type with the basic group characteristics - plants all share an ancestor with simple plant characteristics, but the ancestor they share with fungi is neither distinctly plant or fungus, so they have been designated into different Kingdoms. Based upon this criteria, most zoologists think that the Animal Kingdom should be splintered into at least two Kingdoms. The Protista and the Monera are often "made up" of multiple Kingdoms in advanced books on the subjects.
By this definition, any group should be monophyletic, where every member can be traced from a single ancestor that can be included in that group. If this is not true, a group is said to be polyphyletic, which is a criticism; it implies that multiple groups that shouldn't be lumped together are being classified incorrectly.
Keep in mind, like all aspects of classification, this fits into the convenience of human labeling, which doesn't always comfortably fit what the real organisms are doing. And with that fresh in mind...
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Labels require definitions, and species is a very particular label that has been defined in different ways through the past. It first just meant a distinctly-describable type; then it was distinct types that could not interbreed; then it was distinct types that could breed and produce offspring that themselves could go on as adults to breed (some crosses between species can produce young, such as horses and donkeys producing mules, but they grow up to be sterile adults). Today, the best, latest nontechnical definition of species is...
Species: A group that, in natural surroundings, breeds exclusively within the group.
In effect, we now let the organisms themselves determine what belongs to their species and what doesn't. This still is not a great definition - it says nothing about asexual species. And, like almost any biological definition, it still has exceptions, such as with coyotes, dogs, and wolves. But it works fairly well.
Before long, there may be a strong attempt to define species genetically based upon molecular differences. This sounds simple and mathematical, but it isn't; don't expect a reliable standard any time soon.
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