by Tomo » Feb 23rd, '07, 11:21
I'm quite busy today, so I thought I'd pre-empt "where's the evidence of evolution in the fossil record" type arguments with some real references. I think what this gives more than anything is an insight into the sheer amount of painstakingly detailed work done by countless researchers to find out what, why and who we are and where it all really came from:
TI: Osteolepiformes and the ancestry of tetrapods.
AU: Ahlberg-Per-E {a}; Johanson-Zerina
SO: Nature-London. Oct. 22, 1998; 395 (6704) 792-794..
AB: Fossil discoveries and improved phylogenies have greatly improved
our understanding of the origin of tetrapods, making it possible to
reconstruct sequences of character change leading to tetrapod
morphologies, and to tentatively identify the genetic basis for some
of these changes. However, progress has centered on the upper part of
the Tetrapodomorpha which is occupied by Devonian tetrapods such as
Acanthostega and Ichthyostega. Few advances have been made in
improving our understanding of the lower, 'fish' part of the group,
beyond establishing Elpistostegalia, Osteolepiformes and Rhizodontida
as progressively more primitive constituents. It has not been
convincingly confirmed or disproved that the Osteolepiformes, a
diverse but structurally uniform group that is central to the debate
about tetrapod origins, is monophyletic relative to tetrapods (that
is, a single side branch on the tetrapod lineage). The earliest steps
of the fish-tetrapod transition have thus remained poorly resolved.
Here we present the first detailed analysis of the lower part of the
Tetrapodomorpha, based on 99 characters scored for 29 taxa. We show
that both the Osteolepiformes as a whole and their constituent group
Osteolepididae are paraphyletic to tetrapods (that is, each comprises
a section of the tetrapod lineage with several side branches), a that
their 'uniting characters' are attributes of the tetrapodomorph stem
lineage. The supposedly discredited idea of osteolepiforms as tetrapod
ancestors is, in effect, supported by our analysis. Tetrapod-like
character complexes evolved three times in parallel within the
Tetrapodomorpha.
Or
TI: Ankle morphology of the earliest cetaceans and its implications
for the phylogenetic relations among ungulates.
AU: Thewissen-J-G-M {a}; Madar-S-I
SO: Systematic-Biology. March, 1999; 48 (1): 21-30.
AB: Recent molecular studies are inconsistent with ungulate
phylogenetic trees that are based on morphological traits. These
inconsistencies especially relate to the position of cetaceans and
perissodactyls. Evaluation of the close phylogenetic ties between
artiodactyls and cetaceans has been hampered by the absence of tarsal
bones of primitive cetaceans, as artiodactyls are often diagnosed on
the basis of their tarsus. We here describe newly discovered tarsal
bones that are the oldest cetacean tarsals known. We present a
character analysis for primitive ungulate tarsals and evaluate their
impact on the ungulate phylogenetic tree. Tarsal data are consistent
with some molecular studies in suggesting that the extant sister group
of Cetacea is Artiodactyla or that Cetacea should be included within
the latter order. Tarsal data do not support Cete (Mesonychia plus
Cetacea) and are consistent with the exclusion of perissodactyls from
paenungulates as suggested by some molecular studies.
TI: Locomotor evolution in the earliest cetaceans: Functional model,
modern analogues, and paleontological evidence.
AU: Thewissen-J-G-M {a}; Fish-F-E
SO: Paleobiology-. Fall, 1997; 23 (4) 482-490.
TI: Anatomy and systematics of the Confuciusornithidae (Theropoda:
Aves) from the late mesozoic of northeastern China.
AU: Chiappe-Luis-M {a}; Shu'-an-Ji; Qiang-Ji; Norell-Mark-A
SO: Bulletin-of-the-American-Museum-of-Natural-History. Nov. 10, 1999;
0 (242): 3-89..
TI: On the origins of birds: The sequence of character acquisition in
the evolution of avian flight.
AU: Garner-Joseph-P; Taylor-Graham-K; Thomas-Adrian-L-R {a}
SO: Proceedings-of-the-Royal-Society-Biological-Sciences-Series-B.
June 22, 1999; 266 (1425): 1259-1266.
TI: Postcranial pneumatization in Archaeopteryx.
AU: Britt-Brooks-B {a}; Makovicky-Peter-J; Gauthier-Jacques;
Bonde-Niels
SO: Nature-London. Sept. 24, 1998; 395 (6700) 374-376..
AB: Pneumatization of the postcranial skeleton by the lungs is thought
to be a hallmark of the avian skeleton, and to be an adaptation for
flight by reducing weight. Pneumatic features have, however, remained
elusive in the primitive avialan Archaeopteryx lithographica. The
hollow long bones of Archaeopteryx were first interpreted to be
pneumatized, but this interpretation was later rejected because of an
absence of pneumatic foramina in these bones that connect their
interiors with the respiratory system. Pneumatic features have also
been recognized in the axial skeleton of many non-avialan theropod
dinosaurs (and some other archosaurs of the bird clade). The purported
lack of postcranial pneumatic features in Archaeopteryx has been
interpreted as a primitive condition of avialans; this raises doubts
about the homology between postcranial pneumatic features of birds and
non-avialan theropod. Here we re-examine two specimens of
Archaeopteryx. These specimens show evidence of vertebral pneumaticity
in the cervical and anterior thoracic vertebrae, thus confirming the
phylogenetic continuity between the pneumatic systems of non-avialan
theropods and living birds.
TI: Two feathered dinosaurs from northeastern China.
AU: Qiang-Ji; Currie-Philip-J {a}; Norell-Mark-A; Ji-Shu-An
SO: Nature-London. June 25, 1998; 393 (6687) 753-761..
AB: Current controversy over the origin and early evolution of birds
centers on whether or not they are derived from coelurosaurian
theropod dinosaurs. Here we describe two theropods from the Upper
Jurassic/Lower Cretaceous Chaomidianzi Formation of Liaoning province,
China. Although both theropods have feathers, it is likely that
neither was able to fly. Phylogenetic analysis indicates that they are
both more primitive than the earliest known avialan (bird),
Archaeopteryx. These new fossils represent stages in the evolution of
birds from feathered, ground-living, bipedal dinosaurs.
TI: Ghost lineages and "mammalness": Assessing the temporal pattern of
character acquisition in the Synapsida.
AU: Sidor-Christian-A; Hopson-James-A
SO: Paleobiology-. Spring, 1998; 24 (2) 254-273..
AB: The origin of mammals has been characterized as a gradual process,
a claim based primarily on a well-preserved series of extinct
nonmammalian synapsids ("mammal-like reptiles") that span some 200
million years. In contrast to the origin of many other higher taxa,
the origin of mammals from within cynodont-grade therapsids is not
considered to coincide with a major morphological change, but rather
to be simply the culmination of a series of more and more mammal-like
transitional forms. To test these assertions, an asymmetrical
cladogram extending from primitive "pelycosaurs" to morganucodontid
mammaliaforms was created. Three different methodologies were then
used to compare the amount of morphological change between nodes on
this cladogram with the minimum missing time interval between each
node, as inferred from sister taxon-based ghost lineages. In general,
a statistically significant positive relationship was found,
indicating that greater numbers of derived features tend to be
correlated with longer ghost lineages. A significant correlation
between the number of accumulated apomorphies and branching events
was also found. Although the rate of character change was variable, in
no case was a long ghost lineage associated with few apomorphies.
These correlations are consistent with the hypothesis that rapid
accumulation of derived features occurred relatively infrequently
within the synapsid lineage leading toward mammals and that gradual
character evolution predominated.
TI: Evolutionary and functional morphology of the knee in fossil and
extant horses (Equidae).
AU: Hermanson-John-W {a}; Macfadden-Bruce-J
SO: Journal-of-Vertebrate-Paleontology. 1996; 16 (2) 349-357..
PY: 1996
AB: The hindlimb of modem Equus caballus is distinguished by the
presence of a passive stay-apparatus, i.e., a system of bones,
muscles, and ligaments that facilitate long periods of standing with
reduced muscular activity. Gravitational forces normally collapse
(flex) the knee (stifle) joint. Thus, either muscular activity in the
knee extensors must counter this action, or there must be a passive
"locking" of the knee in extension. The latter situation has evolved
through a complex arrangement of patellar ligaments, medial
enlargement of the patella, and significant enlargement of the medial
trochlear ridge (MTR) of the femur. Together, these elements
facilitate a passive "lock" of the knee joint in an extended Position
without continued high levels of muscular activity. Primitive horses,
such as Mesohippus from about 25 to 35 Ma, have a distal femoral
morphology similar to that seen in outgroups, including tapirs,
primitive rhinoceroses, and most artiodactyls. Specimens of
Protohippus from about 12 Ma represent the first equid clade in which
there is an enlarged MTR. This derived condition of the MTR is
observed thereafter in the family Equidae, despite evolutionary
experiments that included dwarfing or the tendency towards
monodactyly. The enlarged MTR may be used as an indicator of the
existence of a passive knee locking mechanism in the evolution of
horses. Thus, morphologic characters correlated with the knee locking
mechanism were present early (about 11-12 Ma) relative to an analogous
locking mechanism proposed in the shoulder region of the Equidae
(about 3-5 Ma). We propose that biomechanical differences in the
weight-bearing of forelimbs versus hindlimbs may account for the
earlier appearance of a "locking mechanism" of the equid hindlimb.
TI: Morphological transformation and cladogenesis at the base of the
adaptive radiation of Miocene hypsodont horses.
AU: HULBERT-R-C-JR; MACFADDEN-B-J
SO: AMERICAN MUSEUM NOVITATES 0(3000): 2-61.
PY: 1991
The above represents a tiny fraction of what's been found out - not theorised or supposed but actually found out and backed by evidence.
Not only that, but we can also see evolution in action in the form of the response to changes we make consciously in other species such as viruses and bacteria and in the morphology and behaviour of animals as we change and shape the environment.
The underlying concept to all of this is change. Evolution is just random internal change that helps lucky individuals in the next generation cope a little better with random external changes. It runs blindly, and that frightens people. Don't be frightened. Accept your place in the universe, use it as a fulcrum and work to make changes that benefit us all for the time we have left.
