From the abstract of a recent
Science paper '
Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds' (Lee, Cau, Naish & Dyke, 2014):
"The theropod lineage directly ancestral to birds undergoes sustained miniaturization across 50 million years and at least 12 consecutive branches (internodes) and evolves skeletal adaptations four times faster than other dinosaurs. The distinct, prolonged phase of miniaturization along the bird stem would have facilitated the evolution of many novelties associated with small body size, such as reorientation of body mass, increased aerial ability, and paedomorphic skulls with reduced snouts but enlarged eyes and brains."
Its behind a pay-wall, but there are some others that aren't.
Downsized Dinosaurs: The Evolutionary Transition to Modern Birds (Luis M. Chiappe, 2009) is a short (9 pages) intro into the subject of the therapod to avian transition, and its freely available for download.
Again, from the abstract:
"The origin of modern birds from animals similar to
Tyrannosaurus rex is among the most remarkable examples of an evolutionary transition. A wealth of recently discovered fossils has finally settled the century-old controversy about the origin of birds and it has made the evolutionary saga toward modern birds one of the best documented transitions in the history of life. This paper reviews the evidence in support of the origin of birds from meat-eating dinosaurs, and it highlights the array of fossils that connect these fearsome animals with those that fly all around us."
Read. Learn. Enjoy.
I did read, I learned and did enjoy. Thank you for actually taking the time to post something of content instead of making the usual 'we have evidence' claim with no accompanying information.
Unfortunately, the opening sentence of the abstract offers nothing but a claim without underlying support.
"Recent discoveries have highlighted the dramatic evolutionary transformation of massive, ground-dwelling theropod dinosaurs into light, volant birds."
I also read the Chiappe abstract and found nothing identifying the non-bird life form which produced the first bird. Simply saying "dinosaurs" doesn't identify the life form.
The article continues......
"Here, we apply Bayesian approaches (originally developed for inferring geographic spread and rates of molecular evolution in viruses) in a different context: to infer size changes and rates of anatomical innovation (across up to 1549 skeletal characters) in fossils."
I wasn't familiar with the term "Bayesian approaches" and found that it's simply a series of guesses and suppositions used to arrive at a conclusion. Randomness, chance and uncertainty is part of the equation in this approach also.
"Bayesian methods are characterized by the following concepts and procedures:
The use of random variables, or, more generally, unknown quantities, to model all sources of uncertainty in statistical models. This also includes uncertainty resulting from lack of information (see also the aleatoric and epistemic uncertainty).
The need to determine the prior probability distribution taking into account the available (prior) information.
The sequential use of the Bayes' formula: when more data becomes available, calculate the posterior distribution using the Bayes' formula; subsequently, the posterior distribution becomes the next prior.
For the frequentist a hypothesis is a proposition (which must be either true or false), so that the frequentist probability of a hypothesis is either one or zero. In Bayesian statistics, a probability can be assigned to a hypothesis that can differ from 0 or 1 if the truth value is uncertain."
I'm finding the usual uncertainties, could be's, might be's, probably's and 'we suppose' language that always accompany certain evolutionary views.
To continue, from the article....
"These approaches identify two drivers underlying the dinosaur-bird transition."
The mention of "drivers" certainly piqued my interest. Regretfully, no "drivers" were identified in the remainder of the summary nor in the Chiappe abstract you referenced so we still haven't identified the impetus, the 'driver' which produced the first bird from a non-bird (unidentified) source.
But, to continue.....
"The theropod lineage directly ancestral to birds undergoes sustained miniaturization across 50 million years and at least 12 consecutive branches (internodes) and evolves skeletal adaptations four times faster than other dinosaurs."
How? Why? And this is only addressing birds being birds being birds.
"The distinct, prolonged phase of miniaturization along the bird stem would have facilitated the evolution of many novelties associated with small body size, such as reorientation of body mass, increased aerial ability, and paedomorphic skulls with reduced snouts but enlarged eyes and brains."
"Miniaturization"? Again, how? Why? And yet again addressing birds being birds.
The editors summary is interesting also.....
"Most paleontologists agree that birds are descended from dinosaurs. How did such large terrestrial or aquatic animals evolve into small feathered fliers?
Right...how? Now, note the usual phrases and words in the remainder of the summary....
" Lee et al. used two large databases of theropod morphology to explore possible evolutionary patterns that may have driven this dramatic transformation (see the Perspective by Benton). They found no clear pattern of miniaturization across the entire clade of Theropoda. However, several lines of evidence suggested that the lineage leading to birds underwent sustained miniaturization. Within that lineage, body sizes decreased and species evolved faster. They also developed ecological and morphological innovations linked to smaller body sizes."
While the articles were interesting, they were no more than the usual guesses and suppositions, without evidence that ONLY random, mindless, meaningless, purposeless and goalless naturalistic mechanisms produced new life forms. To be fair, they did not actually suggest that particular impetus in the articles....they never identified the 'driver'. But if the impetus was something other than that, the identification of that non-naturalistic impetus would be interesting also.
Again, I do appreciate your response.
