Question 050128a:
Mammals are thought to have evolved from reptiles. The first mammal was
a small, rat-like creature. How sure are scientists about that?
Answer 050128a: Not sure at all. It is right, in many evolution
textbooks, you
will find drawings of a 'evolutionary tree', for example this one.
The mammals are linked to reptiles via a small rat-like animal thought
to be the first mammal. But many of those illustrations show a dotted
line, indicating that scientists are not very sure about the link
between reptiles and mammals. Still, the
drawings are very suggestive.
Nature had an article in its January 13, 2005 issue about recent fossil
findings that strongly suggest that this speculation is wrong.
Quote: (Anne Weil, Nature, p 116, Vol. 433, 2005) "Mesozoic mammals are usually portrayed
as rat-sized, nocturnal prey animals, ecologically marginalized and
contrained from evolving diverse body types ans sizes until the
extinction event at the end of the Cretaceous removed non-avian
dinosaurs from the scene. Two fascinating discoveries of near-complete
fossil skeletons, described by Hu et al on page 149 of this issue, overturn this ourdated view. Neither
is of a small anmammal. One is more than one metre long." (emphasis added)
Here we learn that yet another outdated view was unveiled. Weil
continues:
"These latest findings should trigger another avalanche of questions and
speculation among palaeontologists." (emphasis added)
Please note the significant word "another". It is not the first time
that palaeontologists are faced with difficulties to match the theory
of evolution to the facts.
She continues to reveil some interesting facts, known to scientists,
but not to school book authors:
"Despite the frequently made
generalization that Mesozoic mammals were rat-sized, palaeontologists have known for some time that this
was not the case."(emphasis added)
Why is it then that school books still print the old, outdated and
known to be wrong myth of the rat-sized creature? Because the teaching
the truth would "confuse" the pupils?
But wait, it even gets better. Yes, there were other, older fossils of
mammals. But on what data did scientists base their new theory of
mammal evolution. Let's see what Weil has to say:
"Larger mammals include Kollikodon [ ],
Schowalteria and Bubodens[ ]. But exactly how large these animals were
is a mystery, because Schowalteria is known only from the end of a fragmented skull,
Kollikodon from a partial lower jaw
with three teeth, and Bubodens from a
single tooth."(emphasis added)
Palaeontologists base the evolution of mammals on a single tooth. From
this tooth a whole specimen is "reconstructed". That is breathtaking.
Still, the question remains: how did
mammales evolve? Nobody knows.
