Study pinpoints when bow and arrow came to North America

Radiocarbon results suggest a single origin and rapid diffusion through cultural transition networks.

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[ZenBeam]

With an atlatl, however, they found that they didn't get any greater terminal velocity compared to throwing at a target at the same level as the thrower. Because they do not think this represents a previously unknown modification of gravity , this must mean that the release speed of the atlatl was lower when throwing downward compared to throwing level. They account for this as being the result of relatively poor biomechanics of throwing downward using an atlatl.

I do question how much of the relatively poor biomechanics is due to the downward direction of the throw, versus due to the guard rails on the scissorlift getting in the way.

 

[ZenBeam]

It's interesting that in the last photo the thrower is wearing a safety harness that appears to be anchored to someone sitting on the lift platform. In my 20s I used scissor lifts quite a bit and never really trusted the railings, despite my rational brain knowing they are very secure. Depending on how much slack that harness is allowing it could affect the throw.

I went to the article, and it does have a link to the paper. The harness is attached to the guard rail, and only for the 9 meter height. They don't mention anything either way about whether the harness affects the thrower, but at least the lower heights wouldn't have the issue.

They do talk about the guard rails and the potential for it influencing their results. I'll just quote the relevant paragraph and its footnote, which I think addresses it well:

Although our participants used the javelin and the atlatl/dart under similar scissor-lift conditions, we suggest some future experiments conduct trials without the perimeter safety railing to assess whether this variable somehow influences results. Despite their different physical builds and heights (Kim weight: 63.5 kg; Kim height: 165 cm; Eren weight: 83.9 kg; Eren height: 173 cm) both participants consistently “felt aware” of the guardrail, not wanting to strike their arms against it. While neither participant believes that the railing significantly or substantially influenced his relative performance with either weapon, their awareness of the guardrail, coupled with the fact that guardrails clearly would not have been present in the Paleolithic past², was enough for us to take note and report their observations. Future tests should assess whether the presence of a guardrail in our pilot study was a methodological confound such that it negatively influenced – in some currently unknown way – the biomechanics of atlatl performance, but not the javelin’s. While the rest of the discussion section below considers our results at face value, and there is presently no empirical evidence for such a confound, we wish to be as explicit as possible about potential limitations since to our knowledge an experiment such as ours has not been conducted and there is much to build on.

[...]

2. We can envision, however, some sort of natural equivalent to our guardrail in occasional Paleolithic contexts, such as throwing a weapon from behind a rock or fallen tree.