Note: We are in the (long overdue) process of updating and completing our "Common Questions" pages. As they are updated, the pages will feature shorter text and simpler visual style.
BioLogos promotes “evolutionary creation,” the view that all the lifeforms on earth came about by the God-ordained process of evolution with common descent. The word evolution can be used in many ways, but in biology, it means descent with modification. In other words, small modifications occur at the genetic level (i.e. in DNA) when a new generation descends from its parents. Over many generations these modifications can result in significant differences from the ancestral population. When those differences are beneficial for survival, they can work their way through a whole population of organisms, and if the differences are substantial enough, scientists may recognize those organisms as a different species from their ancestors.
“Common descent is supported by multiple independent lines of evidence, most notably the fossil record, the geographical distribution of species, and the comparison of the genomes of many species.”-
i dont think so. the phylogenetic tree for example is a total mess:
even among eukaryote.
there is also a problems with biogeography and so on:
" Evolution of new forms—what some people call “macroevolution”—takes a very, very long time, as small variations add up over millions of years."-
but what if bilion years isnt enough? we can made simple calculation that give us somthing like 10^30 mutations to add a new system.
@dcscccc We intentionally didn’t use the term “tree of life” for the reasons given by the Guardian article you cite. The metaphor (and it’s just a metaphor–notice the scare quotes) of a family tree, though, works pretty well, because it can account for the cross breeding. Others prefer the terms “bush” or “thicket” but I don’t think those are as visually compelling. At any rate, none of this affects the evidence for common ancestry.
“When those differences are beneficial for survival, they can work their way through a whole population of organisms,”
What kind of differences are beneficial to survival? Variation is random, but Natural Selection is not. Natural Selection is rational and predictable, because it is based on adaption.
“What kind of differences are beneficial to survival?”
All kinds. But the question slightly distorts the nature of natural selection. Mere survival is not the operative advantage that matters in natural selection. That advantage is reproductive success. Obviously, survival is a standard prerequisite for reproductive success, but it’s straightforward to describe traits known to benefit individual reproductive success while hindering survival. Ostentatious sexual displays are often good examples of this. And we can easily picture traits that are “beneficial to survival” but would compromise reproductive success.
“Natural Selection is rational and predictable, because it is based on adaption.”
I agree that selection is predictable in principle, if difficult to actually predict due to complexity in real biological communities. But the second part of your sentence is incorrect. Selection is not based on adaptation. Rather the opposite is true: adaptation is based on selection, and as far as we know is nearly always the result of selection. It is wrong to say that selection is “based on adaptation” for the simple reason that selection is frequently unrelated to adaptation. Purifying selection is one example. Extinction is another obvious example—populations and species can be driven to extinction by the same forces that demand adaptation, which means that adaptation and extinction are just two likely outcomes of selective pressure.
.* Extinction is another obvious example—populations and species can be driven to extinction by the same forces that demand adaptation, which means that adaptation and extinction are just two likely outcomes of selective pressure.*
Instead of discussing events in abstraction we need to look at them as we know them to take place so we can analyze the forces that caused them. Let us take the extinction of the dinosaurs. We know that they went extinct because of climate change, specifically the climate of the earth cooled as a result of natural changes and also the result of an asteroid hit.
The dinosaurs were particularly vulnerable because they were so large, and thus needed large amounts food from lush vegetation or from those dinosaurs that feasted on lush vegetation. As the climate changed, the vegetation became more sparse. There was less for the prey to eat and fewer prey for the predators to eat. The dinosaurs had to adapt or die out, and since they were unable to adapt, natural selection selected them out.
On the other hand mammals were smaller and could adapt better to less available food. They grew fur and other protections. Being warm blooded helped them adapt to the cooler climate.
This what I mean when I say that natural selection is based on the ability of life forms, both plants and animals to adapt. The other aspect of this is that it is ecological change that triggers evolutionary change.
In terms of the extinction of the dinosaurs the change of climate opened up many new ecological niches for flora and fauna. Animals usually followed the plants, and thus diversity grew as the ecology grew, developed, and diversified filling the earth with the stupendous variety of creatures that we know today.
The climate and the face of the earth have been in constant flux. This is the way God though Nature has guided the formation of the environment and fashioned homo sapiens as the best adapted creature to control the world.