Do heavier arrows and bows really kill in ancient warfare?

[RogueOne]

How deeply the arrow penetrates through an animal depends on the arrow's momentum as well as the tip/blade that is chosen. Heavier arrows have more momentum. I have bow hunted and have shot arrows straight through fully grown whitetail deer from 30 meters away. That was using a 40lb draw weight and a draw length of 29 inches. I was also using a broad-head on the end of my arrow.

I do not think that a bow would be an effective defensive weapon against predators. Even after shooting that whitetail straight through heart and lungs, the deer ran for 50 meters before incapacitation. Following up with an accurate second shot is virtually not an option with a bow and arrow in a defensive situation.

If you are legitimately at risk of being attacked by a large predator in your area, it would be more effective to use a rifle chambered for a large caliber.

 

[RogueOne]

I recall reading a contemporary account of some explorers who encountered a party of friendly Indians who did not have guns. They camped together for a while, and the Indians tried to teach the whites archery. None among the whites was strong enough to draw the Indian bows more than a little bit.

I believe it. Those explorers were not archers. The draw weight on my bow as of today is so high that most non-archers cannot draw it fully. I am white, one of my good friends from high school is native American. He is unable to draw my bow, which gave us a good laugh when we discovered it. He's not an archer and has not developed those muscles.

 

[zoobyshoe]

I believe it. Those explorers were not archers. The draw weight on my bow as of today is so high that most non-archers cannot draw it fully. I am white, one of my good friends from high school is native American. He is unable to draw my bow, which gave us a good laugh when we discovered it. He's not an archer and has not developed those muscles.

Yes. But the main reason I mentioned that story was to point out that even "primitive" people were capable of making very stout bows, which, of course, were completely deadly in the hands of a decent archer. In other words, modern bows engineered by engineers aren't more powerful or more effective than what even very "primitive" people were capable of making. In the days when they lived by their bows, their bows were powerful and deadly. They killed buffalo with them; they could easily kill people.

 

[Bandersnatch]

In other words, modern bows engineered by engineers aren't more powerful or more effective than what even very "primitive" people were capable of making.

While there's no arguing that bows that were used in war or hunting were effective weapons - otherwise they wouldn't be used - on the above point I disagree.
A large part of good bow design is in making the energy transfer to the arrow efficient. Anyone can make a 'bow' that is hard to draw - just put a string on a thick stick. So a primitive bow that is hard to draw is not an evidence of high quality or effectiveness. The trick is to make the draw weight translate into arrow momentum in an efficient fashion.
That's why you have those really complex constructions in e.g. composite recurve bows of the steppe nomads, and that's why you have the complex arrangement of pulleys on a modern compound bow.

Regarding the story about Indians, the inability of outsiders to draw the bows might not come as much from great draw weight as compared to bows from other places or periods, but rather from the type of draw used by Indians. They were using 'pinch' draw, which makes it nigh impossible to fully draw any decent-poundage bow unless you have really, really strong fingers. By contrast, when using a Mediterranean draw pretty much the only limitation is in your back muscles.

 

[zoobyshoe]

Anyone can make a 'bow' that is hard to draw - just put a string on a thick stick. So a primitive bow that is hard to draw is not an evidence of high quality or effectiveness.

The Native American bow, at least in North American Plains tribes, was a complex composite bow that could be made from many different materials. It was actually highly engineered. Plains Indians traded all the way to the pacific coast for "whale bone" which was the basis for their bows.

Baleen is a filter-feeder system inside the mouths of baleen whales. The baleen system works by whale opening its mouth underwater and taking in water. The whale then pushes the water out, and animals such askrill are filtered by the baleen and remain as food source for the whale. Baleen is similar to bristles and is made of keratin, the same substance found in human fingernails and hair. Baleen is a skin derivative. Some whales, such as the bowhead whale, have longer baleen than others. Other whales, such as the gray whale, only use one side of their baleen. These baleen bristles are arranged in plates across the upper jaw of the whale. Baleen is often called whalebone, but that name also can refer to the normal bones of whales, which have often been used as a material, especially as a cheaper substitute for ivory in carving.

George Catlin reports the plains natives told him a good bow took over a year to make. They didn't use sticks, except for "bird bows," which were light bows for duck and turkey hunting, and training bows for children. Even a bird bow was a composite bow, however, made from different pieces of wood with the proper curves, bound together with sinew.

The average Native bow was not a "stick," but a cable-backed bow:
https://en.wikipedia.org/wiki/Cable-backed_bow

I have seen South American Native long bows for hunting that were monocoque pieces of wood, or "sticks," so to speak, although they're highly and deliberately shaped to function as bows. They can't be drawn too far without breaking the bow. I think they made do with them because both hunting and combat are at closer quarters in the jungle than on the plains. The English longbow, on the other hand, which was a monocoque piece of wood, was made from the Yew tree, which is unique in its elasticity:

Wood from the yew is classified as a closed-pore softwood, similar to cedar and pine. Easy to work, yew is among the hardest of the softwoods; yet it possesses a remarkable elasticity, making it ideal for products that require springiness, such as bows.[37]

https://en.wikipedia.org/wiki/Taxus_baccata
There was no similarly elastic tree in the Americas that I'm aware of. Regardless, I have an inkling the composite, cable-backed bow is something the natives probably brought with them when they first came to the Americas. The one-piece wood bow, in the absence of yew wood, is just not a very strong bow. All ancient cultures the world over seem to have improved on it with composite bow construction.

 

[XZ923]

Delta Force? Fictional action movie star girl? Can't tell if serious, but sure hope not...

True, if someone's going to bring up Katniss Everdeen's bow, it belongs in Sci-Fi. Next thing you know we'll be discussing the accuracy of Han Solo's blaster. In all fairness though, the accuracy of Katniss's bow has nothing to do with the bow's physical composition. Nowhere in the movies does the bow accomplish a shot that Howard Hill probably couldn't replicate with a basic longbow while shooting The Adventures of Robin Hood (I think, I only saw them once). The weapon's accuracy has everything to do with the fact that it's wielded by the "hero" main character...

Back in the real world though, to the OP's original premise, I would point out that when talking about the use of arrows in warfare, it wouldn't have to be a straight-up kill shot. Arrow wounds would affect the fighting performance of the soldier, making them more likely to die in hand-to-hand combat. Also, medical science in that era was such that a flesh wound could easily cause a potentially lethal infection (especially in the chaos of a battlefield). So there were ways an arrow could kill other than "the string's released, the arrow flies, the other guy drops dead". That's in addition to all the other great points on here that a heavier-weight bow (around the 80 pound and up range) can easily put an arrow through someone's heart.

EDIT
OP, if you're interested in this type of thing (how weapons do their damage) check out the TV show Deadliest Warrior. It was one of my favorite shows when it was on. They use all kinds of instrumentation and test scenarios to study the actual damage weapons would inflict.