gluadys,
FWIW:
The engine is an example of homology in automobiles. We observe that in different species of automobile, evolution has adapted a single structure in response to selective pressures. One. Some vehicles, for example, adapted for towing capacity. This allows them to be more efficient foragers. In such vehicles we observe that their engines contain more cylinders than usual, and that the cylinder volume has been augmented. Two. Others species have adapted for speed, allowing them to evade predators more effectively. Again, we see high-performance engines, but we note that evolution has reduced the vehicle's weight to make it more agile. Three. The most prolific vehicles have evolved superior reproductive capacity. Their engines typically have fewer, smaller cylinders, reducing the energy required to produce offspring. We conclude that many species of vehicle descend from the common ancestor in which the basic combustion engine design first emerged.
Convergent evolution is observed in some of the largest species of motor vehicle. An alternate diet, resulting in an engine structure with significant differences from the engines of the former group, indicates that the diesel engine evolved separately from the gasoline engine. Thus, we conclude that selection pressures, not ancestry, have caused the two to exhibit many of the same characteristics.
As a more recent example of evolutionary adaption, we observe that some of the higher orders of motor vehicle have developed secondary electric engines in response to food shortages and corresponding dietary changes. Further investigation is warranted, but we predict that species containing this electric engine structure will share ancestry with their ancestors. However, if electric engines are discovered in species that do not share ancestry, we predict that more evidence will be found that electric engines evolve independently due to convergence.
Another example of automobile homology is the chassis. We observe the same basic structure in nearly all motor vehicles, indicating that the chassis emerged very early in their history. Evolutionary pressures have adapted the chassis to different circumstances; some are significantly larger and stronger to accommodate a larger species with a more powerful engine. Others are small and light to facilitate agility in evading predators. If we include wheels under this heading, we observe that some species have adapted to have more than four wheels due to an environment where it was advantageous to carry heavy loads.
In conclusion, homology in motor vehicles is an important factor in constructing their family trees. However, we must be careful and not attribute convergent features to lineage.
Edit: This is meant to be a conceptual exercise to indicate how scientific methods used in biology might, in general, be applied to other classes of machines. No technical accuracy is implied.
Well this is a little confusing to follow, because it is filled with reproductive references that don't apply. Since you objected to the biological qualification of reproduction, I asked that we leave that aside.
So the first basic homology you are referring to is the internal combustion engine which is used in most vehicles. It comes with a differing number of cylinders and with different levels of power and efficiency, but is basically the same feature, used in vehicles as different as tow-trucks, racing cars and sedans. Right?
This would seem to contradict Barbarian's claim that the Ford pickup is only analogous to the Toyota pickup, at least in this respect, because they both use the internal combustion engine in spite of their different manufacture.
You also refer to the chassis and to wheels as homologies.
Back to engines, you note the existence of two analogous designs: the diesel engine and the electric motor. One might have mentioned the steam engine as well--and then there is solar power. Also propane and hydrogen and hybrid vehicles. I don't know how many of them use a modified internal combustion engine and how many use something entirely different.
So far, so good.
You note that "homology in motor vehicles is an important factor in constructing their family trees."
I think my next question then is "can we actually construct an automotive family tree based on the proposed homologies?"
Consider, for example, the internal combustion and the diesel engine. It is true that the diesel engine is found most often in large vehicles such as tractor trailers and buses. But is it unique to these vehicles? Are not some smaller vehicles also run on diesel? And are these not in some way duplicates of vehicles using internal combustion?
As for vehicles using electricity, steam, propane, solar, hydrogen, diesel or other fuel---do we not find them in the same type of vehicles as the internal combustion engine is found in? In fact, do we not find the same producers making a two-door coupe with either a straight internal combustion engine or with a hybrid engine?
So where do we get a tree here? Vehicles from the same source may use very different engine types and vehicles from different sources may use the same engine types. Vehicles with different uses may use the same basic engine and vehicles with the same uses may use very different types of engines. I do not see a possibility for any tree at all.
In biology, homology is successfully used to establish relationships. One can count on a certain homology appearing in one and only one group. But it would seem such an endeavour in the auto-motive field would be fruitless.
One other note: all of the engines mentioned have the same basic function. No engine has been modified for any purpose other than providing motive power to the vehicle. In biology we often see homologous features in which the structure is similar, but the use of the structure is quite different. One can hardly imagine functions as different as supporting a jaw and transmitting sound waves; but the inner ear bones of mammals are homologies of part of the jaw structure of reptiles.
I am not sure that the internal combustion engine can be seen as a homology. It is certainly basic to many different vehicles. But it serves the same purpose in all of them--something that is more characteristic of analogy than homology. And I cannot see that it discriminates clearly between types of vehicles the way homologies do in biology. We cannot say of any sort of engine: you will find it in vehicles of type X (or in the vehicles produced by company Y) and in no others.
Instead we seem to have a convergence (by many manufacturers, and for many types of vehicles) on the internal combustion engine, yet it is not a complete convergence, for the same purpose is also served--in very similar, even otherwise identical vehicles from the same company---by different engine types.
And the different sorts of vehicles and engines cross-cut each other in such a way that no tree can be constructed. At best one gets a grid showing how many different engines one can find in each type of vehicle.
My impression is that this sort of categorization does not permit distinguishing homologies from analogies. It is better explained entirely as analogy as one company (and one department within a company) borrows design ideas from others and mixes and matches them in various ways.
Don't be so obtuse. I've been saying all along that there are multiple explanations for homology, not that evolution isn't an explanation. Obviously, it is. (Answer: No, I like beating my wife.)
