How come dogs have four legs, instead of two, like us humans?
Dogs have evolved over time to have four legs because of the advantages it provides them in terms of movement and balance.

Four legs allow dogs to run faster, with greater stability and maneuverability, than they would be able to with just two legs. This is especially important for wild dogs that need to hunt for their food. Having four legs also helps dogs better navigate uneven terrain and maintain their balance when jumping, which is essential for many species of dogs that are used for hunting or herding.

In addition, having four legs also allows dogs to carry more weight than they would be able to with just two legs. This is important for breeds of dogs that are used for tasks such as pulling sleds or carrying packs.

So, in summary, dogs have four legs instead of two because it provides them with greater speed, stability, balance, and carrying capacity than they would have with just two legs. These advantages have helped dogs to successfully evolve and thrive in various environments and roles, both in the wild and as domesticated pets.
Humans also seem to have successfully evolved, and perhaps have thrived even more than dogs.  So having two legs must also confer many advantages.  Can you give one or two comparative examples showing why four legs are good for dogs, while two legs suit humans?
Yes, of course! The number of legs an animal has is directly related to its physical capabilities and adaptations. Both four legs and two legs have their own unique advantages and disadvantages.

Here are a few examples of why four legs are beneficial for dogs:

Endurance: Dogs have four legs, which helps them cover large distances with ease and have a higher endurance. This is useful for hunting, herding, and other activities that require sustained physical activity.

Stability: Having four legs also provides dogs with stability, especially when navigating rough terrain or making quick movements. This stability helps them maintain their balance and avoid injury.

And here are a few examples of why two legs are beneficial for humans:

Freedom of upper limbs: Humans evolved to walk on two legs, freeing up their hands for more complex tasks such as tool use and manipulation. This allowed humans to develop greater manual dexterity, which has been key to their success as a species.

Energy efficiency: Two legs also help humans conserve energy. When walking on two legs, humans use less energy than they would if they were walking on all fours. This allows humans to cover longer distances with less effort, which is useful for migration and exploration.

These are just a few examples, but they demonstrate the unique advantages that both four legs and two legs offer. The number of legs an animal has is determined by a combination of factors, including its evolutionary history, habitat, and lifestyle. Ultimately, both four legs and two legs have evolved to serve their respective species' needs in the most efficient way possible.