Bear River Walnut Ranch/Gilbert Group Walnuts

Wheatland, CA >forms and labels Employee resources Equipment DB: Add New Incident All Incident Log  Equipment List  BRWR Hop Ranch Map   BRWR North Map

Bear River Walnut Ranch is situated in the fertile alluvial fan of the Bear River. The area has a historic link to both the Gold Rush, in that much of the ranch's soil is the product of hydraulic mining, and to some of the earliest large-scale agriculture in California, the Durst Hop Farms. Below you will find information about walnuts: their evolutionary history, their domestication, and their currently known health benefits. Walnuts have a very low ecological profile and tend to be perceived as improving the ambiance of an agricultural area, much like grapes or apples, due to the shade they provide, the local summertime temperature reduction they promote via broad-leaf evapotranspiration, and the aromatic oils they emit around harvest time.

Walnuts evolved to be mammal food, and this likely explains their high nutritive value. Explore the links below to learn about the evolutionary origins of walnuts and how they came to be one of the world's healthiest purely natural food supplements.

Genus Juglans, the Walnut species of the world
The Roots of Land Plants

©2022 the Gilbert Family


Figure 1.Wild Juglans world distribution. Light blue is the projected distribution of walnuts prior to the time of the Persian and Greek empires, although it is uncertain if the actual pre-empire native distribution is more to the east, closer to that of Juglans sigilata (dark blue). ©Bear River Walnut Ranch

Land Plants

Plants (Plantae) Come to Land

Plants obtain energy from the sunlight via photosynthesis using chlorophyll in chloroplasts. Chloroplasts, like mitochondria, have separate DNA from the plant cell nucleus, and it is thought that plant origins involve a symbiotic relationship between a mitochondria-possesing unicellular eukaryote and a variety of blue-green algae (cyanobacterium, a photosynthesis-capable prokayrote) about 1.6 billion years ago (Yoon et al., 2004; Weber, 2010). Plants include non-vascular plants (non-'woody' plants like mosses and liverworts) and vascular plants ('woody plants'). Non-vascular plants colonized land from the ocean about 460 million years ago, and definitive vascular plants are first seen in the fossil record in deposits dating to approximately 420 million years ago (Steemans et al., 2009).



Figure 2. LEFT Non-vascular plant, liverwort Lunularia cruciata (public domain image). RIGHT Primitive vascular plant, the club moss Diphasiastrum complanatum (image courtesy Bernd Haynold).


Vascular plants (Tracheobionta)

Lignin (Lignen) is an polymer that fills space in the cell wall of plant cells. It chemically crosslinks with the plant compound hemicellulose and forms a mechanically rigid, water impermeable matrix in the cell wall. Vascular plants have incorporated this matrix in the development of tissues that transmit water, nutrients from the ground, and photosynthesis products. Vascular plants are rigid and wood-like when dry, and include flowering plants, conifers, ginkos, cycads (palms and kin), ferns, and club mosses.


Seed plants (Spermatophyta)

Seed plants originated approximately 330 million years ago (Simth et al., 2010). Seed plants include cycads, ginkos, conifers, and flowing plants.


Flowering plants (Angiospermae)

Flowers are the most obvious novel adaptation of angiosperms, but fruit, reduced pollen size, and leaves are also major features. Conifers have male pollen cones and female cones. The pollen is carried by the wind from the male cone to adjacent female cones. Genetic/developmental constraints on the conifer reproductive system restrict possible cone forms and thus canalize evolution; all pine cones are the same basic shape, and all must drop pollen in the same basic way. Flowing plants underwent a series of evolutionary transitions during in the later Jurassic and Cretaceous involving seeds, pollen, and leaves, that culminated in rapid series of evolutionary bursts from the later Middle to the Late Cretaceous, from about 120 to 90 million years ago. Many major rosid groups are established by the Late Cretaceous, including Rosales (tree fruit, berries, etc.), the stem of Fabales (which will later diversify into Legumes, alfalfa, clover, etc.), and basal Fagales (birches, alders... this group will later diversify into chestnuts, oaks, and, most importantly, Jugladoideae).


The key parts of the angiosperm reproductive system are the flower, the pollen, and the fruit/seed. The pollen is much smaller in flowering plants (especially true dicots, the ‘Eudicots’) than in conifers, and reproduction often involves long distance wind and insect pollenation. The flower guides the pollen to the ovule; visually, mechanically, or by other means. The ovule grows into the fruit/seed. The fruit has a dual evolutionary role: it both provides nutrition for the pre-photosynthetic sprout and provides food for animals that might disperse it. This means that the form of fruit is often the subject of mixed evolutionary pressures. It 'wants' to be distributed by animals, but it doesn’t 'want' all of the seeds/fruit to be destroyed in the process.


Angiosperms, flowering plants, are first seen just after the Jurassic, about 140 million years ago. Flowering plants initially radiated during the Cretaceous. Placental (non-marsupial) mammals (Wible et al., 2007) and social insects (Brady et al. 2006) originated and began expanding and differentiating rapidly during this period. 'True' dicots (Eudicots; those with tricophate pollen) split from Monocots (grasses and cycads) approximately 110 million years ago. Eudicots are a large, diverse group of plans that includes everything from cabbage to buttercups to roses to walnuts. The major diversification of Eudicot trees, the angiosperm forest expansion that replaces conifers in tropical and temperate areas, takes place in the Cenozoic, the age of mammals.


Animal/angiosperm evolution has been linked in many ways, and many flowering plant lineages have evolved symbiotic relationships with mammals and social insects, exchanging nutritional and medicinal rewards for help with spreading seeds. Genus Juglans, walnuts, is one of these. Walnuts provide a high concentration of nutritious, healthy fatty acids (and maybe other health-promoting chemicals) to squirrels in an evolutionary exchange for help with seed dispersal.




Figure 3. The radiation of broad-leafed forests. Data based primarily on Chase (2009), Soltis (1999), and Smith (2010). ©Bear River Walnut Ranch

References cited


Aradhya, M. K. (2006). Cladistic Biogeography of Juglans (Juglandaceae) Based on Chloroplast DNA Intergenic Spacer Sequences. Darwin's harvest: new approaches to the origins, evolution, and conservation of crops, 143.

Aradhya, M. K., Potter, D., Gao, F., & Simon, C. J. (2007). Molecular phylogeny of Juglans (Juglandaceae): a biogeographic perspective. Tree Genetics & Genomes, 3(4), 363-378.

Bailey, V., & United States. Bureau of Biological, S. (1931). Mammals of New Mexico (Vol. 53): US Govt. print. off.

Blokhina, N. I. (2004). On some aspects of the systematics and evolution of the Engelhardioidea (Juglandaceae) by wood anatomy. ACTA PALAEONTOLOGICA ROMANIAE, 4, 13-21.

Baughman, M. J. and Vogt, C. (2002). Growing Black Walnut. Regents of the University of Minnesota. Downloaded from

Brady, S. G., Sipes, S., Pearson, A., & Danforth, B. N. (2006). Recent and simultaneous origins of eusociality in halictid bees. Proceedings of the Royal Society B: Biological Sciences, 273(1594), 1643.

Chase, M. W., Fay, M. F., Reveal, J. L., Soltis, D. E., Soltis, P. S., Anderberg, A. A., et al. (2009). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Botanical Journal of the Linnean Society, 161(2), 105-121.

Chaw, S. M., Chang, C. C., Chen, H. L., & Li, W. H. (2004). Dating the monocot‚ dicot divergence and the origin of core eudicots using whole chloroplast genomes. Journal of Molecular Evolution, 58(4), 424-441.

Edelman, A. J., Koprowski, J. L., & Edwards, C. W. (2005). Diet and tree use of Abert's squirrels (Sciurus aberti) in a mixed-conifer forest. The Southwestern Naturalist, 50(4), 461-465.

Friis, E. M., Pedersen, K. R., & Schönenberger, J. (2006). Normapolles plants: a prominent component of the Cretaceous rosid diversification. Plant Systematics and Evolution, 260(2), 107-140.

Hafner, D. J., & Kirkland, G. L. (1998). North American rodents: status survey and conservation action plan (Vol. 42): World Conservation Union.

Harvey, P. H., Clutton-Brock, T. H., & Mace, G. M. (1980). Brain size and ecology in small mammals and primates. Proceedings of the National Academy of Sciences, 77(7), 4387.

Hause, B., & Schaarschmidt, S. (2009). The role of jasmonates in mutualistic symbioses between plants and soil-born microorganisms. Phytochemistry, 70(13-14), 1589-1599.

Iljinskaja, I. A. I. i. I. (1990). On the taxonomy and phylogeny of the Juglandaceae family. Bot. Zh. SSSR, 75(792-803).

Kruska, D. C. T. (2005). On the evolutionary significance of encephalization in some eutherian mammals: effects of adaptive radiation, domestication, and feralization. Brain, Behavior and Evolution, 65(2), 73-108.

Manchester, S. R., & Dilcher, D. L. (1982). Pterocaryoid fruits (Juglandaceae) in the Paleogene of North America and their evolutionary and biogeographic significance. American Journal of Botany, 275-286.

Manos, P. S., & Stone, D. E. (2001). Evolution, phylogeny, and systematics of the Juglandaceae. Annals of the Missouri Botanical Garden, 231-269.

Maser, Z., & Maser, C. (1987). Notes on mycophagy of the yellow-pine chipmunk (Eutamias amoenus) in northeastern Oregon. The Murrelet, 68(1), 24-27.

Meier, P. T. (1983). Relative brain size within the North American Sciuridae. Journal of mammalogy, 642-647.

Moller, H. (1983). Foods and foraging behaviour of red (Sciurus vulgaris) and grey (Sciurus carolinensis) squirrels. Mammal Review, 13(2‚Äê4), 81-98.

Molyneux, R. J., Mahoney, N., Kim, J. H., Campbell, B. C., & Hagerman, A. E. (2008). Antioxidant Constituents in Tree Nuts: Health Implications and Aflatoxin Inhibition.

Smith, S. A., Beaulieu, J. M., & Donoghue, M. J. (2010). An uncorrelated relaxed-clock analysis suggests an earlier origin for flowering plants. Proceedings of the National Academy of Sciences, 107(13), 5897.

Soltis, P. S., Soltis, D. E., & Chase, M. W. (1999). Angiosperm phylogeny inferred from multiple genes as a tool for comparative biology. Nature, 402(6760), 402-404.

Stanford, A. M., Harden, R., & Parks, C. R. (2000). Phylogeny and biogeography of Juglans (Juglandaceae) based on matK and ITS sequence data. American Journal of Botany, 87(6), 872-882.

Stapanian, M. A., & Smith, C. C. (1978). A model for seed scatterhoarding: coevolution of fox squirrels and black walnuts. Ecology, 884-896.

Steemans, P., Hérissé, A. L., Melvin, J., Miller, M. A., Paris, F., Verniers, J., et al. (2009). Origin and radiation of the earliest vascular land plants. Science, 324(5925), 353.

Steppan, S. J., Storz, B. L., & Hoffmann, R. S. (2004). Nuclear DNA phylogeny of the squirrels (Mammalia: Rodentia) and the evolution of arboreality from c-myc and RAG1. Molecular Phylogenetics and Evolution, 30(3), 703-719.

Stone, D. E. (2010). Review of New World Alfaroa and Old World Alfaropsis (Juglandaceae). Novon: A Journal for Botanical Nomenclature, 20(2), 215-224.

Taylor, M. D. W. (2010). Cyclocarya brownii from the Paleocene of North Dakota, USA. ARIZONA STATE UNIVERSITY.

Wang, H., Moore, M. J., Soltis, P. S., Bell, C. D., Brockington, S. F., Alexandre, R., et al. (2009). Rosid radiation and the rapid rise of angiosperm-dominated forests. Proceedings of the National Academy of Sciences, 106(10), 3853.

Weber, A. P. M., & Osteryoung, K. W. (2010). From endosymbiosis to synthetic photosynthetic life. Plant physiology, 154(2), 593-597.

Weigl, P. D., & Hanson, E. V. (1980). Observational learning and the feeding behavior of the red squirrel Tamiasciurus hudsonicus: the ontogeny of optimization. Ecology, 214-218.

Wible, J. R., Rougier, G. W., Novacek, M. J., & Asher, R. J. (2007). Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary. Nature, 447(7147), 1003-1006.

Wrazen, J. A., & Svendsen, G. E. (1978). Feeding ecology of a population of eastern chipmunks (Tamias striatus) in southeast Ohio. American Midland Naturalist, 190-201.

Yoon, H. S., Hackett, J. D., Ciniglia, C., Pinto, G., & Bhattacharya, D. (2004). A molecular timeline for the origin of photosynthetic eukaryotes. Molecular Biology and Evolution, 21(5), 809-818.