Hi Walter, you wrote:
>-----Original Message-----
>From: Walter Hicks [mailto:wallyshoes@mindspring.com]
>Sent: Sunday, April 14, 2002 4:46 AM
>I have a question of Glenn (or others). It is not a "debate" but rather
>a search for information.
>
>1.) I had always heard that the basic definition of a species is that it
>cannot interbreed with other species. Yet the discussion of hominids
>seems to have a different definition. The discussion is often one of
>whether or not one homined species interbred with another. If so, why
>are they not just called different variations of the same species?.
Obviously with bones, one can't get them to cooperate and produce fertile or
non-fertile offspring. Interfertility is the definition of a biological
species. This describes the situation best:
"First, a species can change over time. According to this
mode of evolutionary change, a single species exists at any given
point in time but evolves over a period of time. An example is
the evolution of humans. The most likely scenario ofhuman
evolution over the past two million years is a change from a
species known as Homo habilis into a species known as Homo
erectus into our own species Homo sapiens. While a single
species exists within the genus Homo at any point in time, there
is continued evolutionary change such that the most recent forms
(ourselves) are quite different from the earliest forms."
"This mode of species change is known as anagenesis, or
straigh-line evolution. It is illustrated as a straight line, as
shown in Figure 3.7 where form A evolves into form B and then
into form C. Although this mode of evolutionary change is fairly
straightforward, complications arise when considering the naming
of species. Should form A be called a different species from
form B? The problem is that the traditional biological species
concept doesn't really apply. Form A and form B are by are by
necessity isolated from each other reproductively since they
lived at different times.
"Many researchers modify the species concept to deal with
this type of situation. Different physical forms along a single
lineage (an evolutionary line such as that shown in Figure 3.7)
are given different species names out of convenience, and as a
label to represent the types of physcial change shown over time.
Such forms are referred to as paleospecies and are used more as
labels than as units representing the spcies concept." ~ John H.
Relethford, Fundamentals of Biological Anthropology, (Toronto:
Mayfield Publishing Co., 1994), p. 71
>
>2.) Along those lines, I wonder how one can look at hominid bone fossils
>and say there is this species "A" versus that species "B". How much
>variability is there between humans at the present time? There are both
>very small and very tall human populations today. If we were to look at
>"fossils" from exteme examples, would it be clear that they are or are
>not the same "species" as defined above. Would they not be "homo-teeny"
>and "homo-gigantus" to an anthropologist?
Rather than size, there are variations in humans today in which some groups
have more bones than others or different traits. Asians have traits that
differentiate them from other groups as shown below:
"The assumption of regional continuity between East Asian
Homo erectus, archaic Homo sapiens, and modern humans is
primarily based on the presence of clade features which are said
to be characteristic for this region. These include the presence
of shovel-shaped teeth, mid-sagittal keeling, a rounded infra-
orbital margin, a horizontal course of the naso-frontal suture,
Inca bones, metopic suture, maxillary, ear and mandibular
exostoses, and tori. The central problem with regard to these
features, however, is that most of them also occur in recent and
archaic populations from other areas." ~ Gunter Brauer, "The
Evolution of Modern Humans: a Comparison of the African and non-
African Evidence," in Paul C. Mellars and Chris B. Stringer ed.
The Human Revolution. (Princeton: Princeton University Press,
1989), pp. 123-153, p. 143-144
In spite of these differences, we are all one species today. In short, there
is no really objective measure on bones for what constitutes a different
species. As long ago as 1950 at the Cold Spring Harbor conference, Ernst
Mayr suggested one genus including Australopithecines and Homo.
"The biggest bombshell dropped on the Old Guard, however, came
from Ernst Mayr, a German-trained ornithologist and specialist in
the naming (taxonomy) of species in nature. Using the new
yardstick of variability within populations, he stated that
'after due consideration of the many differences between Modern
man, Java man, and the South African ape-man, I did not find any
morphological characters that would necessitate separating them
into several genera.' He suggested that all the fossil human-
like specimens that anthropologists had discovered after so much
laborious effort over the preceding century be simply ascribed to
one genus, our own--Homo. In other words, the entire 'Age of
Description,' from before Darwin to Cold Spring Harbor, was a
waste of time. His opinion was that the differences were not as
great as between genera of other animals. This assertion meant
that the wonderfully diverse lexicon of human paleontology, a
virtual liguistic playground for the classically educated, with
melliferous names such as Plesianthropus transvaalensis,
Meganthropus palaeojavanicus, Africanthropus njarensis,
Sinanthropus pekinensis, Pithecanthropus erectus, and so on, were
to be replaced. Everything was now to be simply Homo, with three
species: Homo transvaalensis, Homo erectus, and Homo sapiens."
"Mayr's proposal went so far that even Washburn argued that at
least the South African Australopithecus be retained (instead of
Homo transvaalensis) because it showed such significantly more
primitive anatomy than members of the genus Homo. Mayr simply
countered that the population is what the species designates.
How one determines a genus is arbitrary. The definition is
gauged by the relative amount of difference that one sees
between the genera of other animals and, in Mayr's opinion,
hominid fossils don't show very much difference. To
anthropologists, this statement was a bit like telling a new
mother that her baby looks like every other baby. It did not go
over well." ~ Noel Boaz, Quarry, (New York: The Free Press,
1993), p. 10
And there is NO definition for what constitutes an anatomically modern human
as compared with an archaic hominid. See Milford Wolpoff and Rachel Caspari,
"The Modernity Mess," Journal of Human Evolution, (1996), 30:167-171, p.
168. They state:
"The main problem with modernity, we think, is reflected in
the fact that there is no worldwide definition of moderns that
simultaneously includes all modern humans and excludes all
archaics. If modern humans share a recent unique origin,
definition of this group should be possible. However, it may not
be possible if the multiregional model is correct." ~ Milford
Wolpoff and Rachel Caspari, "The Modernity Mess," Journal of
Human Evolution, (1996), 30:167-171, p. 169
glenn
see http://www.glenn.morton.btinternet.co.uk/dmd.htm
for lots of creation/evolution information
anthropology/geology/paleontology/theology\
personal stories of struggle
>without it. (G.K. Chesterton)
>===================================
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