Examples of such designoid objects include the hedgehog and the spiny anteater (both of which evolved pointed spines along their back) and the marsupial wolf (which looks like a dog but is actually a marsupial). He illustrates the reason why convergent evolution occurs by using two small models of commercial aircraft. The reason they look similar isn't due to industrial espionage, it is due to the fact that they are both built to fly, so they must make use of similar design principles.
The examples of designoid objects, such as hedgehogs and spiny anteaters, demonstrate convergent evolution due to their shared adaptation for defense. The marsupial wolf's resemblance to a dog highlights the concept, which is further explained through the use of two small models of commercial aircraft. This illustrates that similar designs emerge when different organisms develop traits in response to similar environmental pressures.