Question

I was surprised to see how far apart macadamia and hazelnuts are from each other. I always thought all trees had a common ancestor that was also a tree. But that doesn't seem to be the case? Did wood evolve multiple times?

Answer 1

Wood and secondary growth have indeed evolved multiple times across different plant lineages. Macadamia and hazelnuts, like all plants, share a distant common ancestor, but their woody structures are a result of separate evolutionary paths within the plant kingdom.

Step-by-step explanation:

The concept that wood could have evolved multiple times is indeed correct. Evolutionary thought holds that all plants are descendants of a single common ancestor, a concept known as being monophyletic. Nonetheless, the structural feature of secondary growth, which gives rise to the woodiness of trees, has appeared independently in several distinct lineages throughout plant evolution.

As an example, sizable woody trunks and adaptations to dry conditions in some early seed plants allowed them to thrive in arid habitats, much like modern conifers. On the other hand, the evolution of secondary growth occurred separately in various groups of plants, ranging from clubmosses to horsetails, and seed ferns to the group that produced all extant seed plants including flowering plants, conifers, and others.

The case of macadamia and hazelnuts reflects this evolutionary diversity, as they each derive from different evolutionary pathways within the broad and diverse kingdom of plants. So, whilst they may have very different evolutionary histories, they are related through a distant common ancestor, as are all life forms on Earth according to current scientific understanding.