How does manu smriti has mentions of tribes which were not present at the time of manu?

Question

pauṇḍrakāścauḍradraviḍāḥ kāmbojā yavanāḥ śakāḥ |  pāradāpahlavāścīnāḥ kirātā daradāḥ khaśāḥ || 44 ||

The Puṇḍrakas, the Coḍas, the Draviḍas, the Kāmbojas, the Yavanas, the Śākas, the Pāradas, the Pahlavas, the Cīnas, the Kirātas, the Daradas and the Khaśas.—(44)

The yavanas and sakas are said to be son of yayati the king of lunar dynasty, but manu was the first person in the world how does he know people of these tribes when lunar dynasty was not even established? Is the reson given in any scripture.

Answer 1

I believe the assumption here is that this was Swayambhu Manu who gave these laws but what if the laws are of Vaivasvat Manu that would make these kings quite well known to him.

The very First chapter of Manu Smriti actually mentions that there have been seven Manus indicating that it was probably a work of the seventh Manu:

60. Then that great sage Bhrigu, being thus addressed by Manu, spoke, pleased in his heart, to all the sages, 'Listen!'

61. Six other high-minded, very powerful Manus, who belong to the race of this Manu, the descendant of the Self-existent (Svayambhu), and who have severally produced created beings,

62. (Are) Svarokisha, Auttami, Tamasa, Raivata, Kakshusha, possessing great lustre, and the son of Vivasvat.

63. These seven very glorious Manus, the first among whom is Svayambhuva, produced and protected this whole movable and immovable (creation), each during the period (allotted to him).

Answer 2

If we read initial chapters of Manu Smriti then Manu told other sages that He taught the rules (Manu Smriti) to sage Bhrigu and now he will explain them to you.

In Manu Smriti 1.61, sage Bhrigu said:

स्वायम्भुवस्यास्य मनोः षड्वंश्या मनवोऽपरे ।

सृष्टवन्तः प्रजाः स्वाः स्वा महात्मानो महौजसः ॥ ६१ ॥

There are Six other Manus, high-souled and mighty, who belong to the same race as this Svāyambhuva Manu, and have called into being, each his own offsprings.

In further verses other Manus names also given which means Manu Smriti was recompiled in Vaivasvat Manvantra by Svāyambhuva and Bhrigu though it was created in first Manvantra itself. As it was recompiled in Vaivasvat Manvantra, mention of tribes from this Manvantra not a surprise. On top of that these tribes might have existed in earlier Manvantras too. The thing is, it can have mention of all tribes which happened till current Manvantra and sometimes scriptures mention important things from next Manvantras too.