I was recently asked an intelligent question about the orchids’ closest relative, and from what plant it evolved. If one person asks this, I am sure other orchid lovers wonder too.
Evolution involves studies of the DNA which is arranged into chromosomes in the cell nuclei. The DNA is like the blue print for making an organism. By comparing certain sequences of the DNA, one can create a pedigree based on DNA similarities. This can be tested by making DNA analyses of your family members, including some strangers and foreigners. It will show you are more related to your children, uncles and cousins than to foreigners.
The question of time is resolved by studying fossils, where the age of a fossil can be estimated based on the geological layer it is found, often determined by studying ratios of radioactive isotopes in crystals (they change over time).
This article from 2010, based on fossils and a molecular mutation clock, states that all orchids have one ancestor in common dating back some 77 million years ago:
According to the Angiosperm Phylogeny Group (2009, Botanical Journal of the Linnean Society 161: 105-121), the orchid family ‘Orchidaceae’ is a part of the Asparagus order ‘Asparagales’. This is also based on DNA sequencing. The ancestor of the orchids is extinct so we do not know exactly what it looked like. This ancestor’s descendants were the lilies on one hand, and the ancestor of the asparagus order and the commelinid plants (gingers, grasses, palms and Commelina) on the other hand. Within the Asparagus order, the orchids branched out early, all other families are on the other branch of the pedigree.
The details were published by Davis et al. (2004) A phylogeny of the monocots…Systematic Botany 29:467-510.
To transform the results in a pedagogic way one can make this simplified conclusion:
‘The grand-grandmother of the orchids was the lilies’ (Liliales) and pandan’s (Pandanales) grandmother. ‘The ancestor of the daylilies, asparagus and sandlilies was the orchids’ sister’.