Was Moretum the Inspiration for Pesto?

Short answer
Yes, it is inconceivable that pesto isn't a modern version of the Roman sauce, moretum.

Long answer
There's no question that the recipe we know today as pesto Genovese was perfected in Genoa around the mid-1800s. However, the similarities of the sauce in terms of ingredients, preparation method, and geographical location mean we can be confident that moretum (and, to a slightly lesser extent, agliata) was the inspiration for pesto. Let's look under the bonnet of each sauce.

Agliata
Location: Ancient Rome
First mentioned: 1st century AD
Name: Based on "aglio," meaning garlic
Ingredients: garlic, olive oil, breadcrumbs, vinegar, and salt.

Moretum
Location: Ancient Rome
First mentioned: 1st century AD
Name: Based on the "mortar" in which it is made.
Ingredients: herbs, oil, cheese, vinegar, salt, and nuts.

Pesto
Location: Genoa, Italy
First mentioned: 1863
Name: Based on "pestare," meaning to pound in a mortar
Ingredients: basil, oil, cheese, garlic, salt, and pine nuts.

Despite lacking nuts or herbs, Agliata shares a passing similarity with pesto. Its excessively liberal use of raw garlic (the Romans loved it) would probably be too overpowering for today's palates.

Moretum, on the other hand, is remarkably like modern-day pesto. This sauce was eaten by the Romans in the area we know today as Italy, almost 2000 years before the word pesto first appeared in print.

Some say that Virgil, the most celebrated of the Roman poets, was the first to mention Moretum in a poem of the same name. Some historians aren't convinced that it can be credited to him, but we like to think it was.

The fact that there is such a similar precursor to pesto takes nothing away from the Genovese. They introduced their world-class basil and transformed it into the sauce we all know and love today.