Do native English speakers naturally speak in the 4th tone?
I don't know how native English speakers feel, but my perception is that words like "hard" "luck" are close to the fourth tone when you read them alone.

An interesting fact is that even the tones are the same, the characters are pronounced significantly differently in a passage.

Here is a passage where all characters are of the fourth tone. You may try to read it aloud, or ask a native to read it (naturally, not robotic) for you and record it. Listen carefully to find out the truth.

少帅见利忘义，为庇护政治势力，竟犯上作乱介入内战，酿就事变，太过放肆！后计划泄露，被控告重罪并入狱。

梦碎后，教训历历在目，少帅大彻大悟下放下恶念，落泪叹道：“这就是宿命。现在落到这个地步，部下、后代亦被迫害，若未背信弃义算计大位，境况会是现在这样？太幼稚，太意气用事！”但少帅却未忘咒骂：“怪赵四那贱货，要是未泄密，刺客会被卫队看到？大业会败露？”

这个教训告诉各位，欲干大事，既要注意部队纪律、践诺信义，又要控制色欲、战胜诱惑。若欲占据宋氏幼妹，勿忘后院那位妒妇，是忿恨混入爱意，竟让赵四放弃父辈政治旧怨，暗地助力挫败叛乱。但，事变最后竟是促就抗日战线扩大，就事论事，亦算是个意外获利。

各位，故事就到这，在下快递要到，外面在叫，再会~

Credit to Zhihu user 树神彧