Then and Now

I am sure that, if we were able to visit several widely separated pre-industrial periods, then we would recognize many common features differentiating such periods from ours.

In post-Roman Britain:

"Two guards lounged on the stairs, and snapped to alertness as the agents approached."
-Poul Anderson, Time Patrol (New York, 2006), p. 36.

In Cyrus' Persia:

"Guards, lean lightly armed youths, squatted beneath on their heels because standing at attention had not yet been invented. They rose, nocking wary arrows, as Everard approached." (p. 68)

In the Roman Empire:

"Two sentries stood in the portico. Like those at the gate, they challenged the Patrolman..." (p. 601)

Now those guys were standing and maybe at attention - being Romans.

In Britain in 1250 B.C.:

"A few stood leaning on their spears in front of their leader's tent of striped canvas, standing to attention not having been invented yet."
-SM Stirling, Island In The Sea Of Time (New York, 1998), p. 151.

On the other hand, some human communication is non-liguistic and perennial:

"...others called invitations which Doreen needed no Tartessian to understand." (Island..., pp. 151-152)

Facial expressions, hand gestures and tones of voice would have sufficed. They fall silent when their leader emerges. This also is recognizable, millennia later.