Non-past adjectival participles in Old Tamil

Traditional Tamil grammars have a neat treatment of the adjectival participle, called as peyareccam. Modern Tamil (and so does Middle Tamil) have three tenses – past, present and future. While Old Tamil had only two, namely past and non-past. In Modern and Middle Tamil, we see that adjectival participles are formed from verb stems suffixed with all tense morphemes. Consider:

ōṭ-i-y.a nati

run-PST-ADJ  river

‘River that ran’

ōṭu-kiṟ-a   nati

run-PRST-ADJ  river

‘River that is running’

ōṭ-um-∅   nati

run-FUT-ADJ   river

‘River that will run’

In Modern Tamil, the future tense adjecival participles have come to mean a habitual action and not a future temporal action. This, it seems, is quite a regular semantic change: from a future tense to imperfective aspect. Hence, ōṭum nati means the habitual ‘river that runs’. What is to be noted here is that the future tense adjectival participle doesnot take the adjectival suffix -a but takes only a null allomorph.   

Now, if we look at Old Tamil, it formed its adjectival participles from only two tenses, namely past and non-past: ōṭiya nati and ōṭum nati. There are some interesting adjectival particples that McAlpin cites in his ‘Proto-Elamo-Dravidian: The Evidence and Its Implications (1981)’:

put-i-y.a

new-PST-ADJ

‘New’

put-um-∅

new-NONPST-ADJ

‘New’ 

It might seem counter-intuitive to construe of a state like newness or oldness as a verb, but here it is. The above adjectival participles suggest that states like newness (denoted by the verb stem put-) were construed as verbs formally. So Old Tamil verbs didn’t denote only processes or actions but sometimes they denoted states too.  
Often the final m is elided in the non-past adjectival participle. So we get doublets like putiya and putu in Modern Tamil, which are actually distinct adjectival participles in origin. Similar doublets would be periya and perum.