Motivated by the swampland dS conjecture , we consider a rolling scalar field as the source of dark energy .
Furthermore , the swampland distance conjecture suggests that the rolling field will lead at late times to an exponentially light tower of states .
Identifying this tower as residing in the dark sector suggests a natural coupling of the scalar field to the dark matter , leading to a continually reducing dark matter mass as the scalar field rolls in the recent cosmological epoch .
The exponent in the distance conjecture , \tilde { c } , is expected to be an \mathcal { O } ( 1 ) number .
Interestingly , when we include the local measurement of H _ { 0 } , our model prefers a non-zero value of the coupling \tilde { c } with a significance of 2.8 \sigma and a best-fit at \tilde { c } \sim 0.3 .
Modifying the recent evolution of the universe in this way improves the fit to data at the 2 \sigma level compared to \Lambda CDM .
This string-inspired model automatically reduces cosmological tensions in the H _ { 0 } measurement as well as \sigma _ { 8 } .