The phrase "are often ancient" is correct and usable in written English.
It can be used when describing something that frequently has a long history or is very old in nature.
Example: "The ruins of the city are often ancient, dating back thousands of years."
Alternatives: "are frequently old" or "are commonly historic".
Associations between primary symbionts and their insect hosts are often ancient in origin, and have facilitated the exploitation of new ecological niches by insects [ 1].
Since enzymes involved in amino acid metabolism are often ancient proteins with high connectivities, see Figure 5a and 5b, the absence of genes coding for these enzymes in the genomes of the obligate symbionts/parasites can account for the lack of correlation between connectivity and domain presence in smaller genomes.
Lozenge was first identified on the basis of its role in eye development and is critical for the differentiation of both photoreceptor neurons and non-neuronal cone cells [ 21, 22] Gene clusters, such as the Hox gene complex, are often ancient and are found in animals separated by hundreds of millions of years of evolution.
Abundant miRNA are often evolutionarily ancient [ 20] suggesting important function.
Protein-coding DNA sequences are often phylogenetically ancient, of far greater age than the species that bear them.
(iii) "Protein-coding DNA sequences are often phylogenetically ancient, of far greater age than the species that bear them... ........ -This is, indeed, universally true.
A list of tests and criteria aimed at establishing the authenticity of ancient DNA results was published in 2000 [10], and these criteria are often applied in ancient DNA studies.
Calagione makes more beer with at least ten per cent alcohol than any other brewer, and his odd ingredients are often drawn from ancient or obscure beer traditions.
Not unlike the young, secularizing middle-class Jewish women who sought Freud's help in 19th-century Vienna, Iraqi women are often caught between ancient traditions and personal needs in a rapidly globalizing society — and they are increasingly turning to internists, psychologists and faith healers for relief of just such symptoms.
The Shasta worshippers are often compared to Ancient Greeks who were obsessed with Olympus, or Moses and his Sinai.
If fresco was the technique commonly used in Greco-Roman wall paintings, it would be reasonable to think that ancient Greeks and Romans had a name to designate this technique and to distinguish from other painting techniques used in wall painting at that time, such as encaustic, whose names (wax and encaustic) are often found in ancient literature.
